Best Downpipe for WRX (2002–2007): 4 Top Picks Compared

The best downpipe for a 2002–2007 Subaru WRX or WRX STI is a catted 3-inch unit built for the GD chassis: the Invidia divorced catted downpipe is the benchmark, the COBB GESi catted downpipe is the premium pick, the Tomei Expreme V2 is the maximum-flow race option, and the TurboXS catted downpipe is the value buy with a 5-year warranty. Whichever you choose, budget for a tune — an aftermarket downpipe changes exhaust flow enough that your ECU needs recalibration to run safely and make the power.

What does a downpipe actually do?

The downpipe is the first stretch of exhaust piping bolted directly to your turbocharger. The factory piece is deliberately restrictive — small diameter, tight bends, dense catalytic converters — because it was designed for emissions and noise compliance, not flow. An aftermarket downpipe opens that bottleneck with larger 3-inch mandrel-bent tubing and smoother transitions, letting the turbo exhale with far less backpressure. It is widely considered the single most effective bolt-on for a turbo Subaru: better throttle response, less turbo lag, and meaningful horsepower and torque gains once tuned.

How to choose the right downpipe

Match your generation first. Downpipes are chassis-specific: 2002–2007 (GD) cars differ from 2008–2014 (GR/GV) in turbo placement and flange layout, and the 2015+ WRX switched to a J-pipe design. All four picks below are built for the 2002–2007 WRX and WRX STI — buy the one that matches your car.

Catted vs. race. A catted downpipe keeps a high-flow catalytic converter: cleaner exhaust, fewer check-engine-light headaches, and a more street-friendly setup. A race-oriented downpipe is built for maximum flow on track-focused cars. Either way, check your local emissions rules before buying — performance downpipes generally aren't CARB-legal, so they're not for sale or street use in California.

Divorced wastegate vs. bellmouth. A divorced (divided) design keeps the wastegate's exhaust stream separated from the turbine's as it exits the turbo, reducing turbulence. A bellmouth merges both streams into one wide opening. Both approaches work well — it's a design philosophy choice more than a right-or-wrong one.

Plan on a tune. This isn't optional in practice. An aftermarket downpipe changes the exhaust dynamics your ECU was calibrated for, so a proper tune is what turns the hardware into safe, reliable power.

The 4 best downpipes for WRX (2002–2007)

1. Invidia [02-07 WRX/STI, 04-08 FXT] Divorced Catted Downpipe

The benchmark GD downpipe. Invidia's HS05SW1DPC pairs a divorced wastegate design with a built-in high-flow cat, built from 304 stainless steel with 3-inch (76 mm) mandrel-bent piping. It bolts directly to the factory cat-back or any Invidia exhaust, and it's one of the most widely fitted downpipes in the Subaru world — a safe, proven choice. Invidia [02-07 WRX/STI, 04-08 FXT] Divorced Catted Downpipe — $861.00

2. Cobb Tuning [02-07 WRX/STI, 04-08 Forester XT] GESi Catted 3-inch Downpipe

The premium pick. COBB starts with a CAD-designed cast bellmouth that smoothly merges wastegate and turbine flow, then runs 3-inch 304 stainless tubing into a COBB-exclusive GESi 300-cell high-flow catalytic converter. Two O2 bungs (factory + wideband), a cast stainless tail flange, and an adapter for the factory donut gasket mean it bolts straight to the stock exhaust. Cobb Tuning [02-07 WRX/STI, 04-08 Forester XT] GESi Catted 3-inch Downpipe — $995.00

3. Tomei [02-07 WRX/STI] Expreme Version 2 Stainless Race Downpipe

The racer's pick. Tomei builds the Expreme line for competition use: SUS304 stainless construction with lost-wax-processed flanges and a straight-through, maximum-flow layout. If your GD is a track car or a no-compromise build, this is the one. Tomei [02-07 WRX/STI] Expreme Version 2 Stainless Race Downpipe — $690.00

4. Turbo XS [02-07 WRX/STI, 04-08 FXT] High Flow Catted Downpipe

The value pick. TurboXS starts with a big 4-inch 304 stainless bellmouth at the turbo — larger than most — then tapers to 3 inches downstream, feeding a high-flow catalytic converter. A pre-welded wideband O2 bung, OEM-style donut gasket for a factory-like seal, and a 5-year warranty round out a package that undercuts the premium options by a wide margin. Turbo XS [02-07 WRX/STI, 04-08 FXT] High Flow Catted Downpipe — $616.00

Quick answers

Do I need a tune with a downpipe? Yes. Budget for it as part of the job — it's what turns the hardware into safe, reliable power.

Will a catted downpipe still throw a check engine light? It can. A high-flow cat flows far better than stock but isn't identical to the factory unit, so some cars still flag a catalyst-efficiency code. Your tuner can address it during the tune.

Can I install it myself? It's a bolt-on job, but the turbo studs and hardware on a 15–20-year-old car are often seized. Soak everything in penetrating oil, and source a fresh turbo-to-downpipe gasket before you start — the Invidia, for example, doesn't include the turbo flange gasket in the box.

Which is better: catted or race? For a street car, catted — cleaner and more civil with minimal power sacrifice. For a dedicated track build chasing every last bit of flow, a race-oriented design like the Tomei makes sense. When in doubt, go catted.

All four downpipes above are available through JDMuscle — pick the one that matches your chassis and your goals, pair it with a proper tune, and enjoy the single biggest bolt-on transformation your turbo Subaru can get. Not sure which fits your car? Message us and we'll point you to the right part.