anything from the cat back is just sound man, and youll be dealing with a lot of that
Actually, the exact opposite is true. The current group of headers gain almost no power, and the piping from the header to the cat is 2.5", the biggest you want to go on NA. When it comes to exhausts, however, you can gain over 15hp with a catback (Kazuma), and at least 10hp with an axle back (TPR). Not too shabby.
TPR will come along with the header power soon.
? are you saying that if I leave the cat on I wont loose backpressure?
Nope, the cat is pretty free flowing already and will hardly affect backpressure. If you go to a 2.5" catback, the reduction in backpressure will hurt low end power, but will make for a better flowing top end. The stock midpipe is pretty free flowing already (resonator is straight-through and perforated), so by adding just an axle back, you can gain low end AND top end, and control exhaust noise at the same time.