I would stick with starting off by getting a cold air intake, and changing out some stuff in the exhaust end starting with headers, and full exhaust system. Maybe removing the cat if you don't have those pesky yearly inspections palces to get a new tag. Of course removing the cats is illegal, so my disclamer is "Off road use only!"
Really tho, the cheapest things is to help your car breath easier, and get rid of the exhaust easier. Maybe upgrade your MAF snesor, change to a bigger throttle body, and upgrade the CPU. That seems to be the starting point tho. Maybe switch to some lightweight pullies.
As to be up with a stock GT without going into major induction, you will have to get a NOS set up for that I do beleive. With those mods above, it still wouldn't be enough without the NOS.
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93 5 Pointer. Cobra Chrome Rims, BBK Cold Air Intake, Electric Fan, BBK Headers with H Pipe and Flowmasters, MSD Ignition Goodies.