Just from an old fart's view...
This part was originally in the end of the post, but it was brought to my attention that even though I knew in my head that it is better to do this first, it didnt come off that way in the way it was written...
The FIRST thing to gain power off these cars is to get a better exhaust. Ford corked it real good and one of the best bang for the buck mods is A BETTER EXHAUST SYSTEM. Plus it makes you sound intimidating.
Mods for intake are all over the place, but it seemed by the post that y'all were new to this, so I thought my babbling *** would chime in.
Cold air kits will give you the best gain for the dollar. More so in the realm of sound, but I have noticed some HP gain mostly from the cooler air below the car.
Mac makes a nice looking one and MN12 Performance makes a nice kit if you dont want to spend a lot of money and want something to be mounted below the car.
Ultimately, you will want to open up the intake plenum a bit so you can strap on a 70-75mm throttle body and then accompany it with a matching tube of some kind and a matching to better yet, bigger MAF from C&L. Combined with a cold air kit, this will get you good reaction as well.
If you have the dollars, by all means visit
www.magnumpowers.com and go nuts, you can strap on 60hp EASY with a nice torque gain.
If you have limited funds, start with cold air, but dont get trapped with a small size if you want to go bigger intake tube and TB later to support other mods. Plan ahead so you dont end up taking it in the azz with parts laying around.
If you have the means and a 89-93, then get some kind of cold air kit, bigger TB, bore out the plenum to match the TB, get a raised blower top, overdrive pulley, at least 36lb injectors and a 190lph fuel pump...The C&L MAF will calibrate the EEC to allow for the bigger injectors, but the EEC Tuner from MN12 performance will be the best investment for all future mods you can dream of.
My first mod was the pulley, top and original supercoupeperformance.com cold air kit. I noticed nice results.
I have done it all, bought it all and tried it all (well most of the aftermarket ****) and I dont know enough stats to throw a bunch of jargon around, but I do know how it made the car feel, respond and perform well in my opinion.