Throttle Problem

[BlueHavenKennel]

Hi everyone. We changed the Idle Air Control Valve, which had quit moving and the throttle position sensor checked out fine. We used carb cleaner to check for vacuum leaks per suggestion from my co-workers but didn't find any. So, we just tried turning the idle screw and closing off the butterfly in the throttlebody. And making me feel totally stupid, it slowed down the idle. It wants to idle about 1100-1200 rpm which is still a bit faster than I want but at least its not racing now. Still can't figure out why we had to turn the screw since it wasn't touched when we took the engine out or put it back in. Anyway, this car has a huge throttle body on it. We compared it to the one we took off of my old mustang (an 89 LX with a 5.0) and to one that was given to me off of a 94 with a 5.0 and it is bigger than both of them. Any ideas if that is normal or if not what it came off of? It looks the same, just a larger hole and butterfly. But anyway, she's coming along, slowly but surely. Just replaced passenger side wheel bearings in front so now it's not so mean to drive, and just primered the front bumper. Still have to take a new picture. Hopefully before too much longer we will have her looking more like my old one, only in GT style. LOL.