1992 B2600 starting/accelerating problem
 

Truck will only fire and start cold with throttle body held wide open. Then when engine is hot trying to restart the engine it will intermittently fire only with throttle body wide open but will only start with ether. Once started with timing set to spec engine runs smooth but dies as soon as you touch the throttle. Advancing timing will allow acceleration but runs rough and idle too high. I've triple checked the timing and sent ECU back to AvPro and they found nothing wrong with computer. Any ideas?