1994 Cadillac EL Dorado fuel injector wire harness

I have a low milage 94 eldorado, I love the car but every month or so I have to take it back to the cadillac dealer here in town, it will start missing severely and will blow white smoke out of the tail pipes, every time I take it to the shop they tell me the harness in the motor that goes to the injectors needs replaced, but it is a discontinued part, and they have no way of getting a new one, so they will repair the wire that is causeing the problem and then return my car running great, but about a month or a 1000 miles later it does it again. They suggest I call salvage yards and get a used one, but what if it has the same problem as mine now does? I just want the car repaired correctly, and the dealer here keeps telling me there is nothing they can do, any suggestions?