Yikes! Ive seen this discussion on so many forums. You will gain little to nothing with a cat back system.....only sound. Our cars are equipped with a very well flowing 2.5 dual exhaust system. If a better sound is all you want to achieve, yes, get a cat back..........or, to save cash, just swap out mufflers. If you want hp gains, get long tube headers and cats. And if you have lots of cash just burning hole in your pocket, get a complete system for both hp gain and sound.
Might I suggest getting the headers w/cats and a good tune. Then see how it goes from there.
2010 Inferno Orange 2SS/RS M6, Black leather, Sun roof, OBX Headers, Halltech cai, Mike Norris tuned.
Avenging Orange, 34 years of not buying into the hype!