Basics that will not cost and arm or leg!!
#1 Borla ATAK exhaust Catback, aggressive throaty sound
#2 New CAI, research this, many around, mine was a Halltech Yellow Jacket
#3 Larger Throttlebody, I went from the stock 95mm to 102mm, added quick response + HP
#4 Tuner, many ways to do this, I had a Diablo In-Tune tuner, added much HP, but ultimate is fine tune on a dyno with the Diablo tuner or a better professional tune (costs much, depends)
#5 Long tube headers
This is a good start even with just #1-3 or 4!!