Have you gone over the Intake and Exhaust on your car? If you have not swapped out the LS4 intake mani and stock downpipe/exhaust, putting a bigger cam in is going to cause more frowns than smiles.
I haven't got down in dirty with it yet I have a chance to get a ls1 intake(what else do I need) and exhaust I'm building my own 3inch kit 50 bucks for the stick and 30 to have it welded and bent to specs