If its the same as my W124 M103, you can adust the timing if its a factor of exactly 3 degrees out.
This is done with a resistor on the side wall of the battery area.

If you look on the inside wall where the bettery is (facing the engine) you will see a small plastic cyclinder with numbers and N, and S, marked on it. You can pull out the cylinder and its like adjusting a watch, pull it part way out, line up in the new position, push back in a check.

Good luck.

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