2.25 or 2.5 is the way to go dude... and so is D.C. SPORTS! their exhausts are amazing, they are the best by far, you won't be dissapointed, but you'll have to get one used. it's not that hard i got mine off civicforums for $230 shipped, so you should be able to find one no problem. people mod preludes just as much as civics, but i wouldnt go with anything larger than 2.5" and nothing other than D.C. SPORTS! good luck!