I have a 390 cid FE in my 1972 Ford truck and lately I have been experiencing a problem that I believe is fuel delivery related. When accelerating or going up a big hill if I press on the gas too much it begins to backfire. This backfiring will continue until you let the engine idle for a minute or two. This engine acted exactly this way a year ago when the fuel filter plugged up, I replaced the filter then and had no trouble with it until recently. This time I have replaced the fuel filter, carburator and the fuel pump and still it acts the same. It will run just great until it has a heavy fuel demand placed on it. I'm wondering if I need to go to an electric fuel pump?