1995 Chevy Silverado 95 Chevy Truck idle rough and won't ru

The truck starts fine but idles very rough. Under heavy throttle truck tries to rev up but can’t. If you press the gas pedal to the floor and hold it and then just let off, the engine dies. We have done the following in no order, removed the converter from the exhaust, tune-up, new gas, removed and cleaned the gas tank and replaced all fuel filters.
What could cause this? Remember no check engine light comes on.
Thanks for your help