carb issue with 1982 ford f-150

First make sure not to use ethanol.Next use high 91 octane fuel.Hopefully can fuel up near your home.Once back home place truck in Park.Rev your engine to 2000 rpm and hold this position for 45 seconds to one minute.Sounds like you have carbon deposits on your cylinder walls.Let me know your results

As Felton stated your problem could be in the octane level of the gasoline you are using. Eighty seven octane will not cut it 1980's era vehicles required low to mid 90 octane level fuel. The pre-ignition backfire you are experiencing is due to ethanol having a detonation level lower than gasoline. Check and make sure the vehicle is not backfiring through the carb either. You can seriously damage the internals of the engine if either condition is true.

Thanks, gents.....tank is full right now....can I get away with adding a stabilizer of octane booster to try things out?

Bye passed EGR valve....doing same thing....putting in the fuel stabilizer now....going for another test drive.

Seems like an input to the carb, that comes after the truck runs 20 minutes...and decel still causes slight backfires and engine to stall, however; if I put the truck in neutral at the same time I let off the throttle, idles fine and no backfires...