[DGthe3]

Headers and x-pipe improve the exhaust flow out of the engine, thus freeing up a little bit of power. Under-drive pulleys reduce the work that the engine has to do to turn things like the water pump. An aftermarket camshaft generally changes the torque characteristics so that it can make more power at high rpms, though this often results in a sacrifice at lower rpms. Ported heads improve air flow into (and exhaust flow out of) the cylinder. Air induction generally reffers to cold air induction (or cold air intake, CAI either way). Cold outside air is denser than the hot air under the hood, and denser air makes more power.