black smoke

Manifold cleaning may be required. The catalyst may be full. There may be a problem with the injectors (It may be throwing out excess fuel).

may be from injectors
may be from turbo snail.
engine may be burning oil.

In my opinion, firstly buy a diesel like shell gtl, then add a bidet injector cleaner to it (get a high quality like würth or something), then drive this vehicle with 1 tank of diesel in general, at 2,500 rpm, it would be better if you do a long road. it becomes very sensitive. they cannot spray properly in the smallest dirty diesel, when the spray is not good, the diesel fires black smoke. I think smoke is cut after these processes. Also air filter is very important friends in diesel vehicles especially turbo diesel. Is your air filter clean? because the rich mixture, that is, when the diesel oil is too low, makes black smoke. You can also think of carbon clean. Particle filters are also filled in unused use, and sometimes the institution may be there.