Free up the exhaust with a hi-flow cat and u-bend delete, then add better induction with smaller S/C pulley (3.5" or 3.4") with supporting mods including reprogrammed PCM, 180 t-stat and colder heat range plugs. If you want to go further, then you're going to have to spend bigger money for things like headers, true cold air intake (not one of those cheesy cone filter and polished intake tube pieces of junk) or open up the engine and install longer ratio rocker arms, beefier valve springs, etc.... I would also strongly suggest installing a trans shift kit to help it handle the higher power levels.