2012 6.7L Cummins wont build boost
 

I have a 2012 Dodge Ram 3500 with the 6.7L and all stock for now. Have been experiencing an issue when towing my camper. About an hour in the drive I can not build more than 14 pounds of boost and truck feels like it bogs down when I step on the gas, I have to downshift to 4th gear and then wait a few seconds then the boost will jump up to 35 pounds and the truck will begin to accelerate. It will also do it when I drive around town and have the exhaust brake on and jump on the highway it does the same thing. Very annoying when you are trying to pass somebody. Does anybody have any suggestions on what I need to look it.