i have the kit. im pretty sure it's an 18 inch. imo the kit is worth it, well, not totally, it would have been nice if it was like $350. Anyway, the piping is much nicer, not to mention bigger, it's 3 inches after the muffler. It's stainless steel, and the tip is quite a bit bigger and nicer than the stock one. Looks much better/more aggresive. Plus it is partially perforated (the tip) on the inside of it. I dunno, it's basically exactly the same as the URD 3 inch exhaust. With the catback, an airaid, Urd Ypipe, and a PSC1-003 with a professional tune and dyno ive seen 250 rwhp, 249.8 if you want to be anal. It was 242 before the y pipe
as far as sound, it's pretty loud when you get on it, but that's highly attributed to my intake and ypipe as well. When you're just slightly hitting the gas it's deep as hell, but mellow. Cruising it's really quiet, it's pretty nice. Sets off alarms like no other.
ps: if you cant install it yourself, you may want to consider a fine motor skills class. it's really that easy