Toyota Repair: Stalling, head gasket replacement, toyota celica

Question
I have a 1991 Toyota Celica GT Convertible, approx 145K, 5 spd, 2200 engine.  
Problem:  The car stalls when I come to a stop sign.  After I restart the car it will idle at normal rpm.  The engine runs fine at normal speed, but will stall at the next stop sign.  This usually occurs after the engine warms up, prior to that the rpm will drop slightly at a stop sign but the engine does not stall.  The engine temp is normal and is not overheating.  
Other notes:  The speedometer stopped working prior to this occuring. Further, the engine had overheated and I had the head shaved and replaced the gasket.  The engine ran fine (no stalling) before and after the head gasket replacement.  This appears to be a new problem.  The stalling started to occur after the speedometer broke. I have checked for a vacuum leak or loose hose and could not find one.  I checked the resistance between the  B terminal and ISC1 and ISC2 terminals on the ISC valve, one side seems to be at the incorrect ohms if I checked it correctly.
Any help or suggestions would be appreciated.
Thanks.  

Answer
At this time I would suggest removing the idle speed control valve, remove the entire throttle body and then remove the isc valve and clean it thoroughly, also clean the throttle body on the inside, the throttle body cleaner is available in a spray can at most auto parts places, use and old toothbrush or something like that, a bottle brush also works well, give that a try and let me know if it helps or not.