1986 Chevrolet Celebrity Euro lost power in my car

1986 Chevrolet Celebrity Euro mileage: 194,000 One day I was driving down the road and all of a sudden, I lost power in my car; the only way to keep the car running was to have the gas pedal pressed down. My car still has the same problem and it surges. However, some days I can drive the car just fine and the next day I cannot get out of my driveway. Scanners pick up no codes and four mechanics have looked at my car, even a tune-up specialist. The computer has been replaced but not the PROM - new oxygen sensor - new coolant sensor - EGR replaced - no vacuum leaks - new fuel filter - gas tank cleaned, but the pump was not replaced - a used, but working Throttle Body has been put in - the Fuel Pump pressure and volume has been checked, but only when the car is running fine. One mechanic thinks it's the PROM and the other thinks it is the Fuel Pump. I have spent over $500 on my car; I would GREATLY APPRECIATE your help and advice.