It's a long shot, but I seem to recall someone who had a similar problem and it was cured by changing the fuel filter. Don't recall the specifics, and I know it sounds counter-intuitive; probably related to injection pressure, atomization, and/or timing. Or, it could be my oldtimers disease...
The Constitution needs to be re-read, not re-written!
If you can't handle Dr. Seuss, how will you handle real life?
Current oil burners: MB GLK250 BlueTEC, John Deere X758
New ride: MB GLS450 - most stately
Gone but not forgotten: '87 F350 7.3, '93 C2500 6.5, '95 K2500 6.5, '06 K2500HD 6.6, '90 MB 350SDL, Kubota 7510