The cheapest bang for the buck is Nitrous. For under $600 you can gain an easy 75rwhp on a stock motor with only a fuel pump and spark plug change. The cost comes in when you have to keep filling the bottle. Back in the early 90's we all ran Nitrous until putting supercharges on. I last used Nitrous about 20 years ago when it was $3 a pound. Now I hear it is is tough to get filled in certain areas.
I've put
Vortech's on 4 of my Fox body cars over the years. The first was a basic A trim back in the early 90's on an otherwise stock motor. The problem is you will soon grow tired of just 50-75 more rwhp and want to swap pulleys, etc. Even if you find a good used S trim, you will want to ship it out to
Vortech to have it gone through which costs if I remember about $500. I would never buy a used
Vortech sight unseen unless you know the person. You will also need to decide if you want to use an FMU- which is nothing more than a bandaid that increased the fuel pressure to compensate for not swapping to larger injectors. Once you start going past the base 5-6# of boost you will want to ditch the FMU and then get at least 42# injectors, an adjustable FPR, a 255in tank fuel pump, Fuel pressure, AFR and boost gauges, and you will need a tune. Then factor in a better cooling system- radiator, E fan. Then you will need to address the PCV system with either a check valve, breathers,catch cans to address back pressure. You will want to open up the exhaust with headers, H pipe, cat back. Your stock clutch and flywheel will need to be upgraded, and so on, and so on..
$2k may get you a used S trim, injectors, MAF, but expect to invest at least another $1k to get it dialed in and running properly. I bought my current SC HO trim for $2500 4 years ago with off a guy who had less than 1000 miles on it with SCT80MM MAF, Deka 60# Injectors.Spent another $300 on an Anderson Powerpipe, $500 on dyno tuning, and another $500 on fuel, Boost, AFR gauges, cowl pod and pillar pod holders, SS lines, and another $200 misc crap like fluids, filters. PCV stuff. So probably around $4k buying mostly used parts.
As the old saying goes, how fast do you want to go/spend?