I would suggest that you do a search on this forum for turbo boost adjustment. There is a line that goes from the turbo or the output of the turbo to the injection pump which somehow adds fuel delivery when boost is achieved. There is an adjustment and some other things that need to be checked.

I expect that this is where your problem can be found.

Good luck,

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Larry Bible
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles