I guess I have to poke my nose into the engine area of a newer coach to see what magic they employ.

My guess is that wastegate and controller was required to assure full combustion and that is tied into DDEC. What boost do you show?

The small puff of black smoke now makes perfect sense because the leak in the intercooler caused a loss of boost and you saw the results. Somewhat like when I had a turbo inlet pipe break on my 8V92. That impacted the ability of the turbo to pump air the cars behind me were completely hidden by the black smoke I was putting out.