Well, I can answer your thread very simply because I've been there before with the same kind of mindstate you're in. I bought my 93 four cylinder and wanted to beef it up a little. Let me be the first to tell you that these motors in a NA form will not make any kind of worthwile horsepower. If you ask anyone, the first thing out of their mouths will be the word "turbo". In that case, you'd be better off just buying a 5.0. I'll just list the few things that you can do that help add a few horses, but nothing that will kick your car in the butt.
1. Cold Air Induction- make a hommade Cold air kit out of PVC and get a K/N Panal air filter.
2. Better exhaust- get a header, and either ditch the cats or get high flow ones with free flowing mufflers like Dynomax's.
3. Engine Tuning- tune the motor by changing plugs, wires and other things along those lines.
4. Etc.- I think cams, and other things are available for 2.3's but are costly for what your gonna get out of them. Same with underdrive pulley's. Check out
www.racerwalsh.com for some availbale parts for the 2.3 motor.
As far as keeping it original and modding it......I don't think so. 2.3's make good daily drivers but are not really worth modding unless you go the turbo route. Get a 5.0 or look into a turbo if you wanna mod yer 2.3 but if you want it original, just drive it.