It's very interesting that you posted this thread. I had logged in to post a similar one regarding my '86 SDL (OM603 engine).In my case, the car sat for years and has been getting slowly brought back to life. Not a whole lot of info on the history.

One issue I've been chasing has been an irritating nailing and intermittent soft-miss at idle when the engine is hot. Very similar to yours, with a couple of exceptions - my cam isn't worn and I don't have any reason to believe the car was run with low oil pressure. Otherwise we're in the same boat - known-good injectors, new glow plugs, inspected prechambers, balanced compression (350-360-350-350-360-340), etc.

Mine starts extremely easily, even in the cold weather, and idles smooth until it's warmed up. As the temp starts coming up, so does the nailing, followed by the soft-miss at idle. Anything over 900 RPM and it's smooth as glass. No shortage of power and my 0-60 time is ~12 secs - right about where it should be. Just that irritating nailing and soft-miss.

Very interested to see where this thread goes. We've both kind of tried the same things and are at the same point with a very similar problem, but on different engines (617 vs 603).

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]