Injection pump fiddling is for after the source of compression loss is identified and corrected. Even if the pump were new and calibrated, #2 would be a source of problems because of the extreme low compression compared to the other cylinders. The grey smoke is a clue that fuel is being injected but not burned (low compression).

Put the horse in front of the cart. Find and fix the compression issues then determine if you have problems with the injection pump. It was running before, since you didn't take anything off of it or fiddle with the internal components it should still be fine.

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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]