is there really a noticeable difference in power between 2.5 and 3" exhaust?i want to step up my exhaust size,but i dont want to buy a catback(already have a flowmaster 80 series) and i dont want to have to wait for a 3 inch pipe when i can just go down to a parts store and get a 2.5" Z28 pipe.im also taking out my cat and putting a pipe in its place.

 

Your exhaust is honestly fine with that engine.

 

the flowmaster 80 inlet necks up to 3". just cut the next and get a 3" pipe. MEASURE it first to make sure.
Circumference = pi times diameter