Like I said - I have no experience with the m57n, but there appears to be much information (googled) related to the EGR system & smoking. Just trying to help.

If I relate my 30 + years of diesel experience to the symptoms, I would also check fuel delivery for obstructions/pressure. Are there any fuel screens inline, banjo fittings, etc.?

I have not paid close attention to what has already been discussed in the thread.