[QUICK_EG_B16A]

Yes 2.5" piping should be fine. I think the diameters are the same as far as comparing the n1 catback to the evo but I'm pretty sure the gtspec is bigger. What I would do that would end up cheaper is getting just the muffler (or something close to it) you want, I know apexi sells just their mufflers (even in different colors if you want a different look) take it to a muffler shop and have them do the piping, that way you can do things like eliminate or go to a high flow cat and put in resonators. Seeing as how you live in so cal like me you'll want to keep the dbs down (to avoid the cops) so you may not want to get just a straight through circular muffler, (the oval shaped ones are normally quieter) then you can get a nice tip or leave it for a sleeper look. I got my entire exhaust done with, hi-flow cat, 12" resonator and dynomax race flow muffler with a thermal R&D tip for less than 400 bucks and it looks/sounds nice (similar to street RSR system). I only did 2.25" piping(because I'm going the NA route) so it might be a little more for 2.5" or bigger. But if you truly want a name brand exhaust, I like the sound and looks of apexi more.