smoking diesel exhaust

I’d check the entire intake for blockages, starting at the open end all the way to the intake valves. It’s not a Cummins, but my 2001 VW Jetta diesel has a rodent blocking screen at the intake end under the wheel well. That screen keeps the squirrels out, a good thing, but it also catches leaves and other stuff and can restrict airflow if not cleaned out from time to time. It also has an issue common to diesels with egr systems (as all do now) in the formation of a hard carbon Buildup in the intake manifold down stream of the egr. It is quite possible you have such a buildup, which requires removing the manifold and hammer/chisel cleaning. No parts, just labor, but a lot of that. Or you could need a new air cleaner.

Good luck. Do get it fixed, as the air we all breathe will thank you.