[Fulltiming]

Jim, is your coach a mechanical 8V92 or a DDEC controlled 8V92? If DDEC, are you by an chance running VMSpc? The reason I ask is that the DDEC gets a barometric pressure reading that is one of the inputs into how much fuel is injected into the cylinders. If the sending unit has failed it could cause lots of black smoke all the time. VMSpc will tell you what the DDEC thinks the barometric pressure is.

A turbo issue OR a plugged air filter can also cause excessive black smoke.