Well, NOS is the biggest bang per buck.. but I understand where you are coming from. A good set of heads is what you need, the stock heads are the biggest restriction. Then you will need a bigger maf, tb, intake, and exhaust. Ummm.. this stuff isn't cheap.
To go faster, a set of gears is almost the first thing purchased(there I said it). 3.55s or 3.73s are the most common for street cars. Usually 3.55s are recommends for stick street cars and 3.73s for auto.. but you can decide.
Give us an idea of your budget and we can help you with the parts..
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Rick
My 89lx(updated 11/5/2000)
My 97 Cobra