For Subaru WRX and STI owners, few modifications deliver as dramatic a transformation as a header-back exhaust system. By replacing the entire exhaust path from the cylinder heads to the tailpipe—including headers, downpipe, mid-pipes, and mufflers—you reduce backpressure, improve exhaust gas velocity, and unlock noticeable horsepower and torque gains. Beyond the numbers, the exhaust note becomes deeper, more aggressive, and more distinctively Subaru. This guide covers the best header-back exhaust systems and components available for WRX and STI models, along with everything you need to know to choose, install, and maintain them.

What Is a Header-Back Exhaust System?

A header-back exhaust system replaces every exhaust component from the exhaust manifold (headers) to the rear bumper. On turbocharged models like the WRX and STI, the term is often used interchangeably with "turbo-back," though strictly speaking, a header-back system also includes the exhaust manifold itself. The system consists of:

  • Headers (Exhaust Manifold) – Often upgraded from the factory unequal-length design to an equal-length setup for improved flow and a smoother torque curve.
  • Up‑pipe – Connects the headers to the turbocharger inlet. Many aftermarket up‑pipes eliminate the catalytic converter for faster spool and reduced heat.
  • Downpipe – Connects the turbo outlet to the rest of the exhaust. A high-flow cat or catless downpipe is a key power adder.
  • Mid-pipe and Axle-back – The remaining piping and muffler sections that route exhaust to the rear.

Compared to a cat-back system (which replaces only from the downpipe back), a true header-back upgrade nets the largest power gains because it addresses the most restrictive parts of the factory exhaust. However, because it includes the downpipe, a header-back or turbo-back system usually requires an engine tune to avoid boost creep and to fuel correctly.

Top Header-Back Exhaust Systems and Components for WRX/STI

The aftermarket offers dozens of options, but not every brand sells a complete header-back kit. Many enthusiasts build their system by selecting a set of headers, a downpipe, and a cat-back from different manufacturers. Below are the standout choices for each major component, as well as complete kits where available.

1. Killer B Motorsport – EL Headers

Killer B Motorsport’s equal-length headers are widely regarded as the gold standard for Subaru boxer engines. Constructed from thick-wall 304 stainless steel with a ceramic coating option, these headers flow significantly more than OEM units while eliminating the classic “rumble” in exchange for a smoother, more exotic tone. They also include a crossover pipe that helps balance exhaust pulses for better turbo spool. Dyno results from various shops show gains of 15–25 whp when paired with a matching downpipe and tune. Killer B Motorsport

2. Grimmspeed – Downpipe and Cat‑Back Exhaust

Grimmspeed offers a highly engineered downpipe and cat-back exhaust that are designed to work together as a turbo-back system. Their downpipe features a durable 304 stainless construction, a high-flow G‑Sport catalytic converter, and a unique cast discharge flange that minimizes turbulence. The cat-back (available in polished or ceramic-coated finishes) uses a Helmholtz quarter-wave resonator to cancel drone at cruising speeds without sacrificing volume under full throttle. Together, they cut spool time and raise peak torque by nearly 30 lb‑ft in some 2015+ STI applications. Grimmspeed

3. Invidia – N1 or Q300 Cat‑Back (with R400 Downpipe)

Invidia is one of the most popular exhaust brands in the Subaru community. For a complete turbo-back, pair their R400 downpipe (with or without catalytic converter) with either the aggressive N1 Race cat-back or the more refined Q300 cat-back. The N1 is a straight-through design with dual cannister mufflers that produce an unmistakable raspy roar. The Q300 uses larger resonators and mufflers to deliver a deep, more daily‑driver‑friendly tone. Both systems are mandrel-bent from 304 stainless and come with all necessary hardware. Dyno tests on a 2015 WRX show the R400 + Q300 combo adds around 20 whp and 25 lb‑ft with a tune. Invidia

4. Cobb Tuning – Turbo‑Back Exhaust System

Cobb’s turbo-back system is a complete bolt‑on solution for WRX and STI models. It includes a stainless steel downpipe (with optional high-flow cat), a resonated mid-pipe, and a cat-back with Cobb’s signature mufflers. The system is known for its excellent fitment and consistent sound quality—it’s aggressive when you step on it but civil during highway cruising. Cobb also sells an accessory Accessport tuner, and they provide OTS maps specifically for their turbo-back ex haust, making this one of the easiest “tune-required” upgrades to install and calibrate. Gains are typically 40–60 whp depending on the supporting mods and fuel. Cobb Tuning

5. AWE Tuning – Track Edition and Touring Edition

AWE Tuning’s cat-back exhausts for WRX and STI are available in two personalities: Track Edition (aggressive, straight-through) and Touring Edition (with a patented drone-canceling resonator). Both use 3-inch 304 stainless tubing and are hand‑crafted at AWE’s Pennsylvania facility. While AWE does not manufacture headers or downpipes, their cat-back pairs excellently with any high‑flow downpipe to create a superb turbo‑back setup. The Touring Edition is especially popular among daily drivers who want no cabin drone at highway speeds. Sound clips and detailed dyno charts are available on AWE’s site. AWE Tuning

6. HKS – Hi-Power and Silent Hi-Power Cat‑Backs

HKS has been a staple in Japanese performance exhausts for decades. The Hi-Power cat‑back for the WRX/STI offers a distinctive aggressive note with a straight‑through muffler design. For those who want a taste of that HKS sound with a bit more civility, the Silent Hi-Power uses an internal baffle system to reduce noise without strangling flow. Both systems are made from stainless steel and come with polished tips. As cat‑backs, they require a downpipe and headers to complete a full header‑back system. HKS also sells a downpipe for many years.

7. ARK Performance – DT‑S Cat‑Back Exhaust

ARK Performance’s DT‑S system stands out for its twin‑wall, diamond‑etched tips and deep, refined sound. It uses a Helmholtz resonator to eliminate drone, similar to Grimmspeed’s design, and the entire system is crafted from high‑grade T‑304 stainless. ARK also offers a downpipe for most WRX/STI generations, so you can build a matching turbo‑back system. The DT‑S is particularly well‑suited for owners who want a sporty sound without overwhelming the interior or startling neighbors.

Factors to Consider When Choosing a Header‑Back Exhaust System

Not every exhaust is right for every car or driver. Evaluate these factors before making your purchase.

Material and Build Quality

Most high‑end exhausts use T‑304 stainless steel (austenitic), which is highly corrosion‑resistant and durable. Some economy options use T‑409 stainless (ferritic), which is less expensive but can develop surface rust over time. Titanium systems exist but are lighter and more expensive—they also produce a slightly different sound. Check for mandrel bending (consistent diameter throughout), quality welds, and gaskets/hardware made from stainless or brass.

Sound Level and Character

Subaru’s boxer engine has a unique exhaust note, amplified by unequal-length headers. Switching to equal-length headers (like Killer B) eliminates the classic rumble and produces a smoother, higher‑pitched scream. If you want to retain the boxer rumble, stick with unequal-length headers. The muffler and resonator design also affect volume and drone. Systems with Helmholtz resonators (Grimmspeed, ARK DT‑S, AWE Touring) virtually eliminate drone at cruising rpms, while straight‑through mufflers (Invidia N1, HKS Hi-Power, AWE Track) are louder and often produce some drone.

  • Daily driver: Choose a system with a drone-canceling resonator and moderate muffler packing (e.g., Grimmspeed, Cobb, AWE Touring).
  • Track/weekend car: Full straight-through with minimal muffling (Invidia N1, HKS Hi-Power, AWE Track).

Performance Gains and Tuning

Real horsepower gains from a header‑back exhaust require an engine tune. Without a tune, you may see only small gains (5–10 whp) and risk boost creep with a catless downpipe. With a professional tune (or an Accessport with an OTS map), gains of 40–70 whp are typical on a stock turbo WRX/STI. Always plan for a retune when changing the downpipe or headers. Also note that catless downpipes are illegal for road use in many areas; consider high-flow catted downpipes (like Grimmspeed’s or Cobb’s) for legality and lower emissions.

Fitment and Compatibility

Exhaust routing changes between model years. A 2004 WRX has different flange angles than a 2015 WRX. Before buying, verify that the downpipe, headers, and cat‑back are designed for your specific chassis generation (GD, GR, VA, VB, etc.). Some systems require trimming of the rear bumper cover or relocation of the rear swaybar. Read install threads on NASIOC or IWSTI to see real‑world fitment reports.

In many states and countries, removing catalytic converters is illegal for street‑driven cars. Header‑back systems that include high‑flow cats (such as Grimmspeed G‑Sport or Cobb’s high‑flow cat downpipe) are more likely to pass visual inspections, though they still may not meet strict OBD‑II readiness requirements. Always check local regulations before modifying exhaust emissions components.

Installation Tips for a Header‑Back Exhaust

Installing a header‑back exhaust is a substantial job that benefits from a lift, a helper, and the right tools. However, with patience and careful planning, an experienced DIYer can complete it over a weekend.

  1. Prepare your workspace. A concrete floor, jack stands or a lift (at least 24 inches of clearance), penetrating oil (e.g., PB Blaster), a torch (for seized bolts), and a full set of metric sockets and wrenches are essential.
  2. Remove the old system. Start from the rear and work forward. Soak all nuts and bolts with penetrating oil the night before. Expect rusted fasteners, especially on the downpipe to turbo bolts. A breaker bar and hammer may be needed.
  3. Replace gaskets and hardware. Use OEM or high‑quality aftermarket gaskets (Killer B, Grimmspeed offer copper or graphite gaskets that crush better). Replace all exhaust nuts with stainless steel flanged locknuts.
  4. Install headers and up‑pipe first. When adding equal-length headers, you may need to loosen the engine mounts to wiggle the headers in place. Support the engine during this step.
  5. Downpipe installation. The downpipe is the trickiest part. Ensure the turbo flange gasket is seated properly. A flex pipe in the downpipe (present on many aftermarket units) reduces stress on the turbo.
  6. Connect the cat‑back. Fit all sections loosely before tightening. Secure rubber hangers into the chassis mounts. Then tighten from front to rear to evenly distribute stress.
  7. Listen for leaks. Start the engine cold and feel for exhaust escaping at every joint. A soapy‑water spray will bubble at leaks. Tighten clamps or add sealant (copper RTV) if needed.

Pro tip: Many shops offer a “test pipe” or “cat‑less” option. If you live in an area with emissions testing, choose a catted pipe to avoid hassle later. Also, plan for a tune immediately after installation—do not drive hard without one.

Maintenance and Longevity

Stainless steel exhausts are low‑maintenance, but they aren’t invincible. Over time, gaskets may leak, hangers may dry rot, and tips may discolor. Inspect the system every oil change for loose bolts or rubbing against the underbody. Re‑torque the downpipe bolts after the first heat cycle (50–100 miles). Clean the tips with a non‑abrasive metal polish if you want to keep them shiny. If you drive in winter salt, consider a ceramic coating or a stainless steel underbody wash to prevent pitting.

Conclusion

A header‑back exhaust is one of the most rewarding upgrades you can make to your Subaru WRX or STI. It transforms both the sound and the power delivery, making every drive more engaging. Whether you choose a complete bolt‑on kit from Cobb, a custom build with Killer B headers and Grimmspeed downpipe, or a curated setup with Invidia and HKS, the key is to match the system to your driving goals and local regulations. Always pair your exhaust with a proper tune, use quality hardware, and maintain the system regularly. With the right header‑back setup, your Subaru will sound and perform exactly as it should.