On a near stock car? Not much...
My opinion on performance chips such as "superchips" and the like, is that they are not worth it until you get into moderate or heavy mods and need a new chip burned from a dyno...
Save your money and get some 3.73 gears...
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"The Yellowjacket"
1998 Mustang GT
13.97@103
"Hey, you weren't supposed to be that fast!"- Turbo Eclipse Driver