I currently am running an AEM Cold Air Intake and Magna Flow Exhaust, with a 50 shot of N20. Will I get a more noticable gain if I add only an aftermarket header, or do I really need to do flex-pipe and high-flow cat also? Also, is there anything else in that chain I would need or is it just Header-Cat-Flex-pipe-to Muffler. I don't want to add all that stuff and have my exhaust be too load, it is already calling to much attention to itself by the authorities. Would I be just as well off with say an Underdrive Pulley as opposed to only an exhaust header?