I turned the screw on the bottom of the TB on my 93 GT and now the idle goes up and down from about 800 to 1200 rpm.I turned the screw thinking it would lower the idle but it did not. It was idling about 1200 rpm. Is the throttle body set at the factory ? What is the correct idle for a 5 speed ?

 

Was the idle surging before you turned the idle screw? You might want to use the search feature on the fox section and look up "base idle reset", you'll find threads explaining the steps. Or search "surging", you'll be reading for days. I set my car to idle at 700 , just cause it sounds better with my cam lol. I think it should be 800ish.