Easier to give advice while there...

First, Mercedes specifically advices against the use of ATF as a fuel additive. If it might be an injector something like chevron's techron additive can be used in IDE. BK-44 or something.
Also, I've thought my motor had strange noises and then changed the oil and filter, having them disappear!
Could be just loose carbon in the pre-chamber.

I'm not in the state right now... but when at home in Hurst I can take a look at these things. Are you patched into the local MBCA club? Perhaps a diesel addicted member could stop by and offer advice.

Michael

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Michael McGuire
83 300d
01 vw A4 TDI
66 Chevy Corsa
68 GMC V6 w/oD
86 300E