Get ready for things to go off track, whenever anyone mentions UTG, it turns into a hate thread rather than a help thread...
As for your exhaust, as with anything else, it all has to be balanced. Assuming you're going with a 225, that translates to roughly a 3.6L (close enough) engine which isn't very big at all. And considering you're likely going to be driving it and not trailering it to the track, you probably won't be living close to redline all the time with your car. My guess is that a single 2.5" inch exhaust coming out of a quality header (either 6-1 or 3-2-1) will be both plenty for now and ready for any future (reasonable) upgrades. And even then, some might say that's too big...
Now if you plan on only building a track car or using forced induction then ignore me and go bigger.
