It runs ok until it warms up?
If the car is running fine in closed loop(running using pre determined information from the prom), and then starts stalling when it switches to open loop(running using information from the sensors) that usually indicates the ecm is having trouble deciphering the information from all of the sensors. It's not a cheap fix but it is my best guess from the way you describe the way the car runs.
Good luck and hope this helps.