1999 Toyota Camry intermittent stall

I have owned my 1999 Toyota Camry for three years and now has 96000 miles on it. I recently changed the timing belt and outer drive belt. They also cleaned and lubricated throttle body. Since then, the car intermittently stall. It only happens when I step on the break for a complete stop after driving it for 30 miles or so. It runs fine again after it cools down for a few minutes. I took the car back to the mechanic and have them check the timing belt and they replied that nothing wrong with what they did. The car has to be in stall condition to be able to figure out the problem.

Did anybody has similar problem and can tell me how you fixed the problem? Do you think it has to do with the new timing belt or something else?

Thanks