For a while now I've been getting intermittent smoking on my 78 240D. It can be pretty heavy sometimes, I've had people race around me to get out of the smoke, kind of embarrassing. It's a bluish-black color. Seems like it's the smokiest on my afternoon/even commutes home, but not always, 15miles one way nearly all highway. This morning on the way in I'd get a tiny little puff on acceleration, pretty normal for an old diesel with 320k miles, but that's about it. I get a little smoke on start up but not much. I put new reman Bosch injectors in a couple years ago, though I've run around 20k miles of veg oil through them, and they started nailing a while back. Since removing the system the nailing has lessened but is still there, so I know I need to pull, clean, and pop test them. The intermittent thing has got me stumped. Engine temps are always reaching operating temps right about 90C. I've got plans to adjust the valves, which I do annually anyway, replace the diaphragm in the vac pump, and possibly doing the valve stem seals. I may also try the Marvel Mystery Oil trick in the cylinders while I have the injectors out. Any other thoughts or suggestions?

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