Honestly a good handheld tuner will give you really great results because it'll help transfer the power faster and more efficiently due to being able to tune your auto's shift points. Next I'd put gears, I am a huge advocate for 4.10s especially for an auto. Autos can even go 4.30. Then I'd go for wider rear tires, preferably drag radials.
Those three mods will be the cheapest way to take probably a full second off your quarter time and really "feel" the power of your engine.
Otherwise you'll spend thousands doing internal work or adding FI to your engine.
2016 Comp Orange GT (current)
Aurora - 2002 Boosted GT! (Sold, sadly)