I've been doing more diagnostics and I just keeping getting more and more confused. Part of the reason being that this is a 1985 model year, grey market car, so the wiring is quite a bit different from the later US spec cars, which I'm looking at the manuals for.

I've been holding off on adjusting the EHA because looking at the drawings and operation of it, it really shouldn't need any adjustment, and I think Mercedes-Benz doesn't think so either with their marking paint over the screw heads. So I'm going to hold off on that until I can really prove that is the issue.

One thing that definitely seems off is that the air flow meter position sensor is not getting the 5 volts it is supposed to be getting. This sensor is directly related to acceleration enrichment, so I'm going to look into this more.