The car is a 1976 w115 300D.

I have noticed that the smoke coming out of the tail pipe makes my hand feel slightly oily. Its not extremely thick smoke but i do feel confident with concluding that it is not water vapor. I did do a fuel cleaning operation similar to a "diesel purge" but with sea foam fuel injector cleaner. It didnt help much except with restoring a little power.

I am not sure if i should be focusing on the injectors or the injection pump. Hopefully someone can help me pinpoint the issue.

Thanks in advanced.

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1976 w115 300D