Actually, Vis-a-vis, after reading Squid's explanation to the other member's upshift question and the "umpf" feeling during the regen, a light went on in my head. It made me realize that I had mixed up my huff for an umpf, and that the startup of the regen may have been the cause of the "umpf." It did appear that the sound was coming from the location of the DPF.

Perhaps the solution would be for me to find a nice watering hole along a highway within a 20 minute radius. Then both the truck and I will feel regenerated.