Surge & Backfire Solved

Just wanted to share an experience because it might help someone else. It didn't make sense to me. My wife acquired an 89 XJ 4.0 AW-4 Auto. It has 207K miles but ran great. It started backfiring and cutting out when you dip into the throttle while cruising along. Floor it and eventually it stumbled along caught and wound up. It got worse and worse and eventually all you had was W.O.T. and idle. I thought it was the EGR. On older cars I would have thought that the timing was retarded or the carb adjusted too lean. I replaced the distr. cap and wires and checked the plugs-no change. The MAP sensor tube was shot-I replaced it -no change. I could see the EGR plunger moving. I did the SEA FOAM Throttle body cleanout-No change. I took it to the mech and he kept it a week. Fuel pressure was 13 psi! He changed the fuel pump and it runs great.
I always thought these electric fuel pumps either worked or not- this one limped along just at a low output. Since it was a fuel pump I do not understand the ability to run at WOT but there it is. If you have drivability problems at least think about the fuel pump if nothing else helps.