FWIW, I had a similar issue with my 82 R107 that I chased for months until I did a smoke test and found 7 large cracks in the Air Chamber which was letting way too much air into the system and telling the analog CPU to add more fuel. The part was cheap (under $90) but was about 4.5 hours to tear down and replace. This was after replacing the OVP, O2 sensor, oil temp sending unit, and temp sending unit, and a few other un-needed part replacements.

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82 380SL 41K miles sold, 98 SL500 44K miles, 13 C300 4Matic, 14 CLA-250 4Matic