[Scan999]

Cold air intake (AEM, Injen, Banks, etc.), a free flowing exhaust (cat-back, or muffler swap) and a handheld programmer (Superchips, Bullydog, HyperTech).

What Juday said..... Also forget about fuel economy. The cost of the "basic three" mods would never pay for itself MPG unless you put wings on the T and fly to the moon and back. If you are worried about gas you are in the wrong vehicle but if you want to smoke the pants off most people that pull up to the light enjoy!