-What are the most suggested modifications ("must-haves") for a non-turbo 3000GT/Stealth?
Well there aren't ALOT of things that you can do with the engine of an N/A without making it a TT. Here's a list in steps.
First Stage:
-Testpipe
-New plugs, get NGK coppers. Their great, the only downside is that you gotta change them around every 10k and their cheap as dirt too.
-New wires, MSD one's are great. IPO sells 8.5 Superconductors for 65 shipped
If not you can always get some Accels.
-Make sure that you replace the throttle body and plenum gaskets when you change your wires and plugs.
-Get an air intake. IPO sells them for 65 shipped and it's bolt on comes with filter and MAF adapter. There are a wide variety of filters and air intakes that you can buy, i just said IPO because he sells them for cheap and im looking at his site and saw them lol.
Second Stage:
-Get a 3sx performance pulley. You can either get the underdrive or the one that's the stock size. I personally recommend getting the stock size one because it will do just the same thing that the underdrive will do and it won't slow down your accessories. Again that's totally up to you.
-Get a good clutch, maybe ACT or some others, there's a pretty good variety of them. But make sure it's a good known and can handle a decent amount of ft/lb. RPS is also a great brand preferred by our members.
-You should get an aluminum flywheel, most likely Fidanza or something of that sort.
-Lower your car with Intrax or Eibach. These are springs and if you want flexible you can go with TEIN, or some other brand like JIC. But Intrax springs work great and their pretty cheap.
-Get some support on the front and end of the car, what the heck am i talking about? Well get a front strut bar and rear strut bar, thse will help alot with body roll and increase cornering capabilites. If you have the extra cash then also get some sway bars.
Third Stage:
-Exhaust, there are MANY different types of setups that you can do. You can get an aftermarket exhaust or go to a shop and have them make you a custom setup like Fireman or Wicked. You can find more details about these setups
here
-Downpipe, 3sx sells great downpipes.
-New motor mounts, the old ones should be all flimsy by now. If you start your engine and it looks like its gonna come out and bite ya in the ass then get some new mounts. 3sx, and Maximal Peformance sell them for a good price.
-Aftermarket cam gears
Stage Four:
-Ah the wonders of Nitrous. If you need that extra kick then I suggest going with a 50 shot and see how it goes, if the engine responds well than go up to 75. There are tons of brands like NOS, Venom, etc. Thanks Joltsword for the add on
-If you need more power then go S/C. Supercharge your car with one of RIPPS kits.
-Or you can always go TT.
This list was compiled pretty quick, if anybody has anything to chime in please post it and i'll add it.