Originally Posted by Slo86GT
Cat back or just a muffler?
I'm trying to figure out if the 2.5" catback from an ST, modded to fit, would be a better choice than the standard 2.25" model for the N/A cars currently...
The 2.5" would have a lower restriction than the 2.25" tubing, however if you go too large you reduce the backpressure too far and start to hurt performance.
Its been discussed that the 2.5" might be a better plan if you are planning on adding additional power adders down the line. If the limit of your modding is an intake and exhaust and nothing else a 2.25" exhaust may work better.