[majek5]

Read that if you have a bigger downpipe it will hurt the performance. Designed to work well with cai and cat back. Why would this be? BTW if anyone wants one, I can make you a heck of a deal!

[cleatus12r]

I'd like it. How much?

As far as bigger downpipes go, it all has to do with the flow dynamics in the pipe. Gasses expand as they cool and the transition to a larger downpipe actually causes the exhaust to cool too quickly and lose momentum in the pipe. This forces the engine to work harder to force exhaust out of the pipe as well as through the turbocharger so there is more restriction at low engine speeds and cooler EGT.

Is it something you'll feel in your "seat of the pants dyno"? Not likely.