I'm assuming it's the 3.1L V6...
Get a header for it, or look into having one made. Add a high-flow cat to that, then a decent cat-back system. The header collector, cat piping, and cat-back piping/muffler should be 2.5" (roughly) for a 3.1L.
An intake can be made for CHEAP, less than $100 if there's no kit out there. Then you can have your stock throttle body ported out. Also, take apart your intake manifold/s and have them smoothed and gasket matched or possibly extrude-honed.
You could probably find a new set of pistons, and if your lucky - rods, to up the compression for NA or lower it for forced induction. Have the crank knife-deged to reduce a little rotating mass. Then, balance the whole assembly.
Go on the hunt for some cams and anything else velvetrain related, but you'll have less luck there if you can't even find the common (i.e. headers) stuff for it.