2edgesword wrote:
I wondering if it's the result of the system going through the regeneration cycle.
regen won't trigger a power reduction.
Did the Check engine light come on? If so did you read codes?
Even if check engine light didn't come on, try reading codes and see if there are any pending codes or stored codes.
Overheating, overtemp on the tranny will trigger power reduction, but it doesn't seem from your description that was the case.
look in your diesel suppliment in the owners info, It has a section on what can trigger a power reduction.