The Turbo XS downpipe is largest downpipe on the market. The TurboXS downpipe for Subaru WRX and STi features a large 4 inch cast steel bellmouth. From there it tapers to 3 inch stainless steel piping towards the end. It also includes a pre-welded 02 sensor bung for an aftermarket wideband O2 sensor.

Turbo's work best when there is large pressure and temperature differential across the turbine wheel, and having a large free flowing downpipe like the Turbo XS gives you that large pressure and temperature differential. The Turbo XS downpipe fits all 02-07 WRX or STi, and will fit perfectly with Turbo XS external wastegated uppipe.

IF YOU ARE NOT USING A TURBO XS EXHAUST, YOU WILL NEED TO USE THEIR CATBACK ADAPTER PIPE (SOLD SEPARATELY) TO MAKE THIS DOWNPIPE FIT UP TO A 3" CATBACK EXHAUST.