I'm running an 89 5.0 with Explorer intake and efi in a 62 Falcon. I have to give it either to start. It runs rough and backfires when cold. Once warm it runs ok but the idle will sometimes settle at 1500 to 2000 rpm and it surges like a fuel starved carb above 4500rpm. It doesn’t have any codes that are unexpected. No emmisions are installed. Codes...81,82,85. I also have a 15, ecu memory voltage loss, but I have a master kill switch for anti theft and drag racing. Problem started over the Summer. I got it hot 230 coming home from work one day. I put a better electric fan on it and thought I was good. After the runnig hot was solved it would surge at above 4500. I checked my fuel pressure regulator and found I could only get 45psi if I cranked up the pressure. It would run at 60 when I first installed the efi, thus the adjustable regulator. I put a new pump pickup guage assembly in and it is adjusted to 38psi. Problem still persisted. It fried a pertronix flame thrower coil so I replaced it with a Bosch wich lasted all of an hour run time. I read here that TFI and PIP problems can kill coils so I got a new distributor along with plugs and wires and a new foxbody coil. I've thrown alot of parts at it trying to fix it. I've gone through the idle surge checklist and all checks ok. Compression is good. I was thinking injector(s) but have no way to test other than the long screwdriver against the ear.