Aline- yes a 2.25 exhaust should be plenty. the above poster is correct in saying bigger is not always better. and yes magnaflow and flowmaster etc.... all try and build into the muffler what they think optimum backpressure should be. most of the time a quick e-mail to the manufacturer will get you a ton of correct info. they want you to buy the right stuff just as much as you want the right stuff. And while I realize not every company is like this, magnaflow and such have huge reps to uphold and try to keep the high standard. Any time I have had to deal with flowmaster or edlbrock or anything like that when buying parts for a 483 cube big block chevy car, they are more than helpful. I hope this helps you out. I try and stay out of the advice game.