I had an issue with rough idle and a slight stumble off the line. Not sure if it would help your situation but its worth a try as its easy as.

I pulled out the MAF and cleaned the element. I did this simply by spraying it with isopropyl Alcohol and let dry. I also did the same for the dirty temp sensor and clean the butterfly valve in the throttle body.

Issues resolved by doing this included:

-Rotten egg smell after WOT.
-Hard cold starts
-Rough idle

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1985 190E - Gone
1989 230E - Gone
1995 C200 - Gone
1993 280E 120000KM - Built like a brick, the best one yet