Chances are that you will never be able to get the whole story of what happened to your car (I have a similar situation with my '87) but you could try asking the dealer anyway. The other thing that I would do (and do for my car) is to find someone with a "perfect" [unmodified] engine bay and go over it with a fine-tooth comb, photographing and comparing it to yours. Then go through yours, piece by piece, and put as much back to factory stock as you have time and pocketbook for. Things like replacing the SAE bolts with metric should not be difficult. Having the correct parts on the car makes diagnosis a lot easier in the future.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970