Welcome. It seems like electrical for sure. Can you check all grounds and make sure nothing is off? Double check all connections to/from the ECM? Any work recently? Batteries testing good?
Welcome. It sounds like the Banks system is derating the power, likely a built in safety feature. Have you contacted banks to see if they can shed some light for you?
Welcome! Sounds like you take care of the truck.. I might suggest reading this section for some more tuning options.
https://www.ecodieselram.com/forum/forums/ecodiesel-performance.28/