I would definitely try these other things first, BUT. . . I also have heard that running a tank of biodiesel will reduce particulates.

If those things don't work, you may want to consider your timing chain. If stretched enough, you will have lower mpg and increased smoking. Since you don't have to do valve adjustments like we poor OM617 guys, you may not have checked the stretch previously. If you're up in the 4-5 degree range, your timing could be sufficiently off to cause some of your problems.

__________________
Tjohn

82 300 SD
77 450 SL (gone)