1995 Toyota Corolla Engine rough idleing/stall while AC run

Good Afternoon to all and thank you for your willingness to answer my question.

I have a 1995 Toyota Corolla w/181141 miles and I recently had a timimg belt change (12/22/09 at aproximately 175K miles). About two months ago the car started to idle roughly and even stalled if the air conditioning is on or running. I tried to switch the car from drive to neutral at stop lights/sings to avoid it from stalling. While the car/engine does not stall at higher rpm's it does hesitates. I am afraid that the repir shop that performed the timimg belt chage might have done a poor job. The timing belt did break while the engine was running and that was the reason for its replacement. The shop that replaced the timing belt checked the engine with a compression test to deterermine if any valves were broken or bent as result of the broken timing belt and the results of the compression test were negative so no head job was performed. The car did not at any time before the timing belt chage had this or any other type of engine problems. Any ideas of what the problem(s) could be? Thank you so much for your answers