The Perrin one-piece catted downpipe features 3" polished stainless steel piping, with a diverted wastegate design for optimal flow. Perrin's wastegate diverter separates exhaust gases behind the turbo and channels them into the exhaust path further downstream to reduce turbulence and improve performance; resulting in smooth, optimized performance. Perrin's STI high-flow catted one piece downpipe utilizes a single 49 state legal catalytic converter to keep you emissions friendly while improving power at the same time.