"Reduced engine power"

[hatt]

Is there anyway to do a custom tune to prevent the truck from going into this mode? It looks like finding the actual cause is going to be difficult. It's my brothers truck. 06 2500HD with 6.0. Runs great except for this issue which will about get you run over on the Interstate. Pull over and turn off the truck and it runs fine again. Throttle body(local shop said that was the problem along with needing all 8 coil packs replaced) has been replaced but that evidently wasn't the problem.

Truck is bone stock.