I have to agree that a V8 is the best answer if your going for balls out speed...however if your just looking for a quick get around towner....then your next step should be to complete the exhaust. Best bet with hard to find items like that is to call up Ed at 'Gearhead' in Dunedin. He can usually find anything, especially domestic. From there, youll notice driving around town is a bit easier on the throttle and a little nicer sounding. If you wanna push it a little further, get a Hypertech Chip, preferably Stage II. These little wonders make a world of difference at full throttle and youll notice you go from sluggish to peppy rather quickly. From there, if it is a 4.3 Liter, spray it with a 100shot and dont waste your money on anything else because it will just be a trivial waste. If its smaller than a 4.3, well then your pretty much out of luck because I wouldnt run an ounce of Nitrous on a 4 cylinder Chevy Motor from the factory. Hope this helps out a little bit, I give you this info from to many wasted dollars and years of personal experience trying to make Chevy Trucks fast. It is possible though