changing the exaust voids your warranty.
sometimes too much flow will acually decrease the horsepower. Usually open or unresricted is used at the dragstrip when the rpms is going to stay at redline. Alot of exaust companys claim gains that arent true.
not sure on this, but catback means replacing the system from the cat converter back. Its not a performance thing. Seen many motorcycles with so called performance exaust acually lose power over the stock system. The amount that you do gain is not worth the price they are charging for these systems. If you just want the noise , remove the resignator and replace with a nice custom bent tailpipe and put your stock tips back on the end of it. You will get the loud sound your looking for. for hundreds less. If your not modifiing the air intake system, turbo, and computer, your not going to gain anything much other than noise and less gas mileage. THIS DOES VOID YOUR WARRANTY ACCOURDING TO MY VW DEALER!!! (any mod)