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I have the plenum off my 89 right now and I just went out to look. I don't see a single wire in the location you show on my car. At least I havent found it. I can tell you that I have no wire of anykind running off my egr VALVE is that is what you are referring to. The wire you show doesnt look long enough to reach to the back of the head though. Not much help here I guess but I will take a better look tomorrow with more light and see if I can spot mine.
looking at the photo you have posted the egr solenoid seems to be removed and anyway there's only the double connector shown in the pic that goes to it.the egr valve has no electrical connector only one vacuum line.I believe what your looking at is the connector for the AIR system control valve(diverter and check valves)which is also missing in your photo.