My 1991 N/A is idling really high. Between 2800-4000 is its idle. I even turned the idle screw all the way down, and it dropped only to 2800-3000. I checked for vacuum leaks, there was none. Wat else could it be?

 

Check throttle plates or stuck throttle cable...place to start anyway.

 

Check if the BAC is leaking - just pinch the hose with some pliers.
If the speed goes down - it was leaking.

There should be some slack in the throttle cables.

 

did you check under the UIM for vac leaks?