Toyota Repair: 1989 Celica GT, intake hoses, srew

Question
I have a newly acquired 89 GT that stalls about 35% of the time when the clutch is pressed in depending on engine temperature.  The RPM's drop to around 500 and will sometimes just keep dropping.  Turning the A/C on will always keep the motor running and will stop the stall if the A/C is turned on in time.  The A/C returns the idle speed to 800-900 while the clutch is pushed in and if the A/C is turned off the engine will always stall.

Answer
The most common cause is an intake air leak, check all the intake hoses for any cracks or leaks, there should be an idle adjustment srew on the throttle body, it may have a small rubber plug on it,remove the plug and turn the screw to increase the idle speed.