For understanding that "upper screw, lower screw" idea, have a look at this pictures in this post:
http://dmctalk.org/showthread.php?10...l=1#post152181
You can see it best in the 3rd and 4th pictures. The bracket holding those two screws (upper to engage the microswitch, lower to bottom out or come to rest at a zero point/curb screw) pivots together with the butterfly valves that are inside. As Dennis was saying, you want the lower curb screw to rest against its stop right where the butterfly valves are fully closed (i.e. in a vertical position). Once you're happy with that, adjust the upper microswitch screw to just activate the metal tab on the microswitch and then make it protrude perhaps another quarter turn or so.
When you're sitting at idle at a red light or intersection, you want the microswitch to be engaged at the same time the butterfly valves are completely closed and not letting any air by them. What I think can happen to change things slightly (and inconsistently), is if your pivot point and linkage aren't cleaned up well or lubed to some degree, the resistance normally put on by that spring to get it to go back to zero is countered by grime or rust or whatever and then it doesn't come all the way back.
This seems to happen more when the engine is warm or hot which is either affecting the spring or the grime by it expanding or swelling in the heat or it's being affected by the vacuum system somehow getting stronger as the engine has warmed up. This "sticking" idle is what you'll be dealing with if you need to "snap the gas" to get it to come back down. If giving the accelerator a quick snap or two to get it to come down works, then something in that throttle assembly and linkage isn't rotating freely. If the high idle is perma-stuck at 2,000 RPM or something similar, it's generally going to be an electrical connection gone bad.
Speaking of which, you mentioned your connector on that microswitch. Do you have a manual trans? I think you do, wasn't sure though. The automatics also have a "full throttle microswitch" which is very similar in terms of the switch and connector and it is mounted on the side of the throttle spool at about the 10 o'clock position looking down on it.
On the automatics, if you hammer the gas say in 3rd gear while out on the highway pulling out to pass someone, it will kick down the trans to 2nd to give you some more oomph to pass. I don't think the manual trans cars have this microswitch but I think they may still have the connector (not sure about that though). Some owner before you might have confused the two microswitches or connectors to explain why yours was unplugged. Hard to say though for sure.