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The black smoke will rich air fuel ratio. one of the first things to check will be any restrictions in the airflow system first.after which it will need to be checked via diagnostic/live data to route out any stored codes or problems with any engine sensors .then leading to a check of the operation of the fuel/injector pump & re-check of timing and injector seals..
There are few things that can be checked but provided that not always possible without somesort of diagnostic being carried out..
the fuel system is delivering too much fuel into the engine or there is not enough clean air (oxygen )