Hey Tsx owners....I need an idea on what I should tell my exhaust guy on saturday. He is installing an injen sp cai also. He carries magnaflow, flowmasters, and some other muffler that looks like a flowmaster and he claims its one of there better selling. He probably gets the best list price for it. So I need to know if I should do a cat back system or if I should leave the pipes on the car and just throw the mufflers on it. Also I read a lot about the resonator being taken out on these cars and have not been convinced yet. I am looking for HP and performance. Please help me . Thanks for your time.