I am in the process of buying a 2008 LTZ Crew cab Silverado withthe 5.3l. I am looking at the GM Performance Parts Air intake and the GM perfromance Cat Back Exhaust side out ( I want to keep my spare tire). Does onyone have experiance withthese ona 2008? Whould I be better off going with a Volant and a Flowmaster cat back sytem? What are the pro and cons? Pro: GM product GM warrenty. Con: Less performance??????