Bad EGR cooler?

[Chamberpains]

Do you own a laptop with Cummins Insite? Hook it up and monitor the parameters that show derates while operating the truck. That will expose whether its actually derating. Also check all sensors and make sure they are operating within spec. Just because a sensor is new does not mean the circuit is reading correctly. Could be a bad wire, connector or wiring that is creating more resistance than the 5 volt signals can accurately report on.

If you don't have Insite, why not? All the $$ and time you've spent on this problem or possible problem (because its possible nothing is wrong and its all in a misguided "feeling" something is wrong) would've paid for itself and a whole lot more.