[SuperCarrera]

I could really use some guidance with an exhaust issue I am currently dealing with.

On my supercharged 964 C4, although I've never dynoed it (AWD dynos are few and far between!), I'm thinking it's currently around 375 HP (on street gas) with the large intercooler Whipple blower on the 3.6 liter motor (I currently have a single pipe 3" exhaust system throughout with stock manifolds, a cat bypass pipe, and a single Bassani muffler).

To alleviate the slightly excessive noise (for street use) with this set-up, I'm considering an alternate performance muffler but, due to the constraints of my pipe configuration and larger size of this new muffler, I've been told that only a 2.5" (pipe opening) muffler size will work.

My question is this -- with my current (overall) set-up, will this 1/2" reduction make any difference in my vehicle's performance?

If not, as a follow-up question, when I go to headers, larger injectors, and a mass flow air sensor upgrade, should I then (definitely) go to dual exhaust or will the future 400-425 HP output still be OK with this one reduction to 2.5"?

Thanks...

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Tim O'Neill
1989 964 Super-Carrera 4
Sarasota, Florida USA