Jesus...people.
You have a GT? Get a 3" Catted Downpipe (with the U-Bend Delete), put a glasspack in place of the stock resonator or LEAVE it there. Then, buy mufflers of your choice. IMO, Borla's sound tinny and Magnaflow's sound like ass. Let the flaming begin but if you do it RIGHT...read DO IT RIGHT. Flowmaster's sound pretty damn good.
Pacecrapper headers, cammed, 3" Custom Exhaust, stock GM res., no cat into Flowmaster 40 Series Mufflers.
YouTube - GTP Exhaust
And to the tard who said take out the RESONATOR...ARE YOU RETARDED? I bet your car sounds like a pile of crap. I have a resonator and no cat...and there is NO RASP. At all.