The black smoke is likely oxygen starvation leading to partial combustion as you suspect. Before spending money replacing EGR or Turbo, thoroughly check the inlet system between the air intake and the turbo in case there is a blockage, including the intercooler if one is fitted. I once saw a plastic cup blocking an inlet that had blown up from the road on a truck system.
At a really basic level it could be that the hose has become weak with age. If there is no blockage and the pipe has not perished, then you need to check the functioning of the egr valve.
Not sure about the airflow meter or the Turbo.