The original problem was the sealing of the pins in the socket. Early AMP plugs had the pins cast in place relying on the plastic sealing against the pin in the injection process.
Over time with heat, the pins along with capillary action caused the oil to pass from socket to the external plug and wick along the external harness.
This was solved some time ago with a new plug on the injector harness which is relatively cheap and is generally widely available thru aftermarket sources such as Paddocks etc etc. Just look for anyone advertising as a modified unit.
Be aware that it may take some time for the external harness to clear itself and although you flush it and clean the ECU, it will still pass oil lodged in the harness for anything up to 12 months as was in my case.

