1990 Ford F-150 Truck dies while driving, won't restart unti

Hi. Have replaced virtually every electrical part under the hood except for Throttle Position Sensor, Distributor Pickup and EGR valve. Truck starts immediately when cold, but dies while running, usually within 1 mile or less. Won't restart until engine is allowed to cool down, varying in time required from 15 minutes to an hour. Occasionally dies while driving; then while coasting in gear to a stop, truck restarts on its own and often runs for the rest of the day without problems. On really hot days (above 95 degrees), truck will not start at all until the evening when outside temperature has cooled down below approximately 80 degrees. Ford garage has not been able to detect the prolem. Appreciate your help.