I had this same struggle a while back with my 450 SEL. I changed the timing chain, tensioner and the upper rails, since there was a considerable slap of the chain at startup.

I think the chain slipped one tooth at the right bank during installation. So I corrected it at the end before joining the chain. It ended being a little late at the timing mark. I then put it one tooth forward then it was a little early. I put it back to the late position, since that was closer to the mark. I drove for a few days, and everything was fine (the motor got a whole lot silent). But there was something wavy on the motor tune, but I am not sure if it was only psychological.

But I figured it was wrong and I opened the cover and put it one tooth forward again at the right bank. (Left bank was always correct and exactly at the timing mark) . And it was a little early relative to the mark. I think now it ran better. As the chain stretches it should get closer to the correct position.

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MB 350 SL 2.8 -72
MB E220 -95
MB 230 E -82
MB 450 SEL -80 (project)