Quote:
Originally Posted by arwin
I've specifically asked this question to vf engineering before and their response was always that I needed an aftermarket exhaust.
Would like secondary clarification though
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When most people hear exhaust, they usually think of a cat-back, but a downpipe is part of the exhaust "stage." Aftermarket exhausts are really no less restrictive in terms of back pressure / exhaust flow than stock. But trading the stock downpipe for one with a high-flow cat, or no cat at all, allows for decreased back pressure / increased flow. Tuners can take advantage of this by having boost levels taper less quickly at higher RPMs since there's less load on the turbo and motor. If you ran VF's Stage 2 map with the stock downpipe, you likely wouldn't cause any immediate damage, but the increased heat levels and stress on the turbo itself would definitely shorten its lifespan. Bottom line, you only need to upgrade your downpipe for VF's Stage 2 tune. This is supported by the very first post in this thread and the fact that the Stage 2 dyno plot was done with the stock cat-back and an ER downpipe.