I heard a different tune playing from the Cummins. Very faint, but different. It was the same engine sound that usually comes out, but off time.

Slight studder/flutter at easy acceleration.
Check Engine Light appeared only to dissappear.
Intermittent hard start. Missing with a "pop" during start.
Different sounds than I am used to.


Sounds and feels fuel related to me. Maybe an injector.

 

Drain the fuel bowl (or maybe even change filters) and give it a good dose of Power Service. This would be a good start.