slightly larger than 2"....something like 2.3__" as for mufflers, get a universal one of your choice. jic and magnus motorsports make a cat back and turbo back respectively in case you wanna go that route. otherwise, just go custom and get what you want.
depends on what size piping you're gonna go with. if you're gonna stick with stock, i'd say get that axle-back from memphisracer...you know, the one AGR#7 is so enthusiastic about save yourself a 100 bucks and go that route. if you're gonna change the piping size, go with whatever size you need. there's all these arguments about whether to go with 2.5" or 3" so read up and talk to people and make up your own mind. me, i'm going 3".