-a more reasonable question to ask is how much horsepower do you want to make? wihtout detailing a proposed setup and boost level, etc it's hard to guestimate how much horsepower you would make- as for the kits, the XS engineering kit claims to make 237 horsepower at 10psi (CARB legal trim), the Turbonetics kit claims to make 250hp at 8psi, the greddy kit claims to make 225hp at 7.8 psi- of course these are manufactures claims and may be a wee bit high, but that's a general idea- Each of the kits include different things, but the best thing that you can do is check each of the manufacturers websites, read their charts and see what is included in each setup-
-some things to look at are exhaust manifolds- manifolds welded up from mild steel tubing will typically cracj after a few thousand miles or hard use, but an equal length tubular manifold wedled from stainless steel typically flows better and produces more horsepower than a cast manifold, however chances are that a good cast manifold won't crack- Other things to look for are the style of fuel enrichment the kits uses, whether an intercooler is included and if there is any fabrication needed besides attaching a bung for the oil return line to the oil pan-