2.5" exhaust system or 3" exhaust system....backpressure?

[.Lex.]

If your car does not NEED (as in its not making a lot of power) 3" exhaust system (down pipe, cat, pipes), and you install one, will this harm your performance? Do you lose backpressure? I was just wondering, because say your car in current state is running pretty much stock and you want to install an exhaust system 1st, and maybe later on you will run a bigger turbo, maybe not, would installing a 3" be better on a pretty much stock 1g or would a 2.5" provide better results?

Thank you.

 

[Mason]

From what I've read and seen if your going for about 400 hp go with 2.5
If your going with more than 400 than you want a 3" system.

 

[Dieselboy]

Theres no reason not to go with 3". Yeah, 2½" only goes so far, but why settle for less? Back pressure is not an issue as it would be with an N/T.

 

[PropXprt]

IMO if you dont plan on going big then dont get the 3" becuz jeeeesshhh o wiz did I have boost creep from the demons when I installed a full 3" system on my previous dsm; it made the car no fun to drive. next time around I will go with 2.5" dp and 3" catback, and hopefully there wont be so much creep. CREEP = Major PITA "personally"