>The units that have prolonged flame shooting from the stack with prolific black smoke are usually suffering some sort of gross over fueling, due to failed injectors,

Not really possible because the C-B type engines use individual Bosch jerk pumps to generate the for the high pressures for the injectors, and each one is driven by a separate cam. The same is true for Alco diesels.

> or something that is letting oil through the turbo and combusting from the hot exhaust gasses.

Usually black smoke is an underperforming turbo, although it could be from a turbo bearing leak (into the intake manifold). Black=soot, and soot is combustible if you have the right soot/air mixture ratio.