I think white smoke would be a bigger concern...
Start by checking your breather tube for excessive smoke. If you see any then you can do a crank case back-pressure test (to see if your rings are bad).
* More likely Black smoke probably means oil is getting in to your combustion chamber. (Assuming your engine is running almost normal.) You just need to find out where the oil is coming from.
I would first inspect the oil line leading into your turbo. And look for oil on the outside of your turbo.
The hot air coming out of your Turbo is sent to the inter-cooler (that's the radiator looking thing... not to be confused with your engine radiator, which is larger.) So if your turbo bushings are getting wobbly, the seals are gone too, or just the seals are gone, and oil is leaving the turbo and is getting passed into the Charge Air Cooler (CAC) jackets, which are very small, the oil will clog up your CAC and then you have a big expense to remove it... clean it... or you might have to replace it. (Test it first.)
If you need to replace your turbo, this is a sticky wicket. Theoretically, you can find turbos in the $600-$800 range, but Cummins wants $1,500 and you can't get a Cummins authorized repair outfit to put someone else's turbo on... and then you run into guarantee issues. I don't know what CAT will charge for a turbo, but they are known for charging more than Cummins! (As if that is possible? ...And I am told: "Yes it is!")
I would go to a qualified diesel shop and not a dealer. They may or may not treat your pocket book with more kindness.
* If you loose your turbo... and metal goes flying into your CAC then that's the end of your CAC. ($$$) It's just a radiator like device, but a lot of work to get to in most RVs. ...Sort of depends if your radiator and CAC are side mounted or not.
*** Now some good news:
My ECM and fuel injection system failed. $9,000 later I was rolling down the road again. The engine ran well enough, but my white painted Toad had lots of black smoke on the front passenger quarter panel. And prior to these repairs I never had this problem.
This went on all summer. I couldn't figure it out. Then I switched from running Rottella 5w-40 Full Synthetic Oil to Chevron's Delco 400 15w-40. And no more black smoke! ...My guess is that the synthetic 5w-40 oil was getting past the turbo bushing every time I accelerated. I have 75,000 miles on my turbo when this occurred. So hopefully this story fits your situation too?
I now have my turbo on my watch list. But I keep putting off the repair. My MP is also 23-24PSI when I think it should be up to 25PSI. (Your turbo MP maybe different.)
So if your power is down going up hills, look for any cracks in your the boots that feed your turbo air intake and CAC, etc. Plus you don't want dirt getting sucked in that is not filtered air. ...You can tell if you have cracks/leaks because your air tube will be very dirty!
Good luck. Let us know how you fare.
2004 Itasca Horizon ISK-40AD, 350HP Cummins 8.3L
115K miles and the best of 3 Diesels I have owned thus far!