1990 Ford F250
This is the EGR vacuum regulator (EVR). The plug is broken and the contacts won't stay in the plug (red arrows). The wires with their crimped terminals simply pull out. Someone shoved the contacts into the plug but reversed, and that makes the truck run really bad. (Misfiring and no power at low RPM.) A new pigtail was $31 which is crazy, but I replaced it anyway. The EVR tested as marginal, so I replaced it.
I've tried fixing some other plugs where the contacts won't stay in by putting hot glue in there. I don't know if that is a long term fix. Epoxy would probably work better than hot glue.
Also replaced: MAP sensor, EGR valve, EGR valve position sensor, one of the vacuum reservoirs, spark plugs and wires, driver's side rear brakes, slave cylinder, emergency brake cable, ignition switch, and the alternator. I think the passenger side rear slaver cylinder is about to lock up, so that's next, along with the passenger side ebrake cable.