Dies every time you let off the gas, when it's over 90 degrees outside

[daygoxtra]

I drive on a rural mail route and every summer when it gets over 90 degrees outside, my truck will stall and most of the time, will die, whenever I stop or let off the gas to slow down. Sometimes it will backfire if I try to accelerate to keep it running. I does this after driving for an hour or two on my route, having to stop and go quite often. If the temperature drops below 90 outside, it will quit doing this. I have replaced the MAF, IAC, o2’s, fuel pump and the fuel filter. 2000 explorer sport 4wd