The Invidia catless, divorced wastegate downpipe for the 2008 Subaru WRX is designed to replace the restrictive, OEM two piece, two cat, downpipe. Invidia made the 08 WRX downpipe from mandrel bent 3" stainless steel and welded on a thick flange and a cast stainless steel housnig to provide maximum airflow and improved performance. A divorced wastegate downpipe has a plate the protrudes into the turbo to separate exhaust flow coming out of the turbo to give reduce turbulence. This is good for stock and smaller turbochargers.

Invidia's catless downpipe will cause a Check Engine Light (CEL) on your WRX. While this isn't harmful, it can be annoying and disables the cruise control -- you can use a software solution such as the Cobb AccessPORT to eliminate these codes or try a mechanical fix (O2 sensor spacer). Boost spiking may also be a factor, which can be controlled with devices like the AccessPORT.

A divorced wastegate (V3) vs. a bellmouth design (V2). The DW sucks all the wastegate air from the turbo through an alternate path which eventually routes back into the DP while the V2's bellmouth sucks all the air from the turbo.