I have a 94 f150 with a 302. It started backfiring through the intake. I replaced plugs, wires, distributor, sensors , and a lot of other things. Basically all of the obvious. Reset the timing. Each time doing a test run and nothing seems to work. But, on the last run I forgot to plug in the map sensor and the backfiring stopped. But now it idles rough in reverse and stalls out before you can back up. Even with the map sensor plugged in. It drives great and idles fine. It’s just reverse that has the problem. Any help would be greatly appreciated. Thanks in advance