[Mike Gerber]

Since it starts and runs well cold, 2 things come to mind. One is the O2 sensor. This is out of the loop until the engine reaches a certain temperature. Then it comes in to play. The other thing is the coolant temperature sensor. Toyota calls this an ECT sensor. It may be out of spec and telling the car's computer that the engine temperature is always cold. This would produce a rich mixture. A rich mixture is fine for a cold engine but could cause the problems you are experiencing on a warm engine. You will need a manual for the specs and a DVM to check these 2 things out.

Mike