I agree with bounty; if you want mods for a 4banger, check the site (both of us are also members there). You will find anything from superchargers and turbos to the ussual of the mill engines there...
For me, the best one is the e-Fan conversion. I went the junkyard route, and bought a Ford Motor Company '90s taurus fan for under $30 (complete with shroud) and used a DC Controller connector, which controls the fan speed according to temp. This means that (1) it shuts the fan off when on the highway (since the fan is not spinning, there is less parasitic drag on the engine), (2) the fan does not come on at full speed, but the speed is increased slowly, so it pulls few amps (I used it with the stock alternator for about a year without issues even with the auxiliary lamps and the stereo amp), and it turns the fan on at low speed when the AC compressor is on. I also have a backup system wired to the low-speed wiring of the fan using a relay, but I have not used it for the 2-years the fan has been on except when I want to test it. I should point out that the FoMoCo fan is more powerful than the Flex-a-lite fans (some estimate the output at around 4,000 CFM!).
My second choice would be the 62mm 4.2 TB and spacer. I got the chore from a junk yard and got it bored, but Bounty can sell you the complete thing.
You can also use a K&N or Airhog filter for the stock box, and this will help a bit. But just dont expect HUGE improvements (the only way you will feel the change is on the highway, where you will not need to downshift as often as before). All the mods mentioned are good, but work better when added one to the other...
The best mod (but out of your $1,000 budget) is to regear. But that one will be expensive (especially if you are like me and dont know how to do it yourself).
Felipe
