CAI, Headers If you have an 05-06 model,The rest of the exhaust,good sparkplugs,Tune.
If you really want get into Port and polish the Cyinder Heads and Intake manifold.
Also
New fuel delivery systems $,$$$
ignition system Like MSD? not really need and also $,$$$
Turbo or supercharger You can but you will need to beefing up the trans,If you Did under 4lbs of boost you could proably get away with a shift kit, regular fuild chages and a Heavy duty cooler.... For awhile but it will take 3k to do right just for the trans. $$,$$$
intake manifold