My CEL is on so I return the truck to stock about a week ago, drop it off at the dealer for a new EGR valve. Takes two days to finish and about two hours after I pick it up the CEL comes back on. Run the DTC and it comes back to the EGR valve. Bring it back today and have them do the EGR system de-carb. Less than 20 minutes after I leave, it comes back! Call and talk to one of the services people. Get put on hold and she comes back and says..."Your check engine light is on cause I'm holding your air filter". Apparently the tech took it off to show me how dirty it was and forgot to put it back on. I ask about the turbo being dusted and am told not to worry about it.
Also, the diesel tech said the ECU "showed" I had a tuner at some point and wouldn't upgrade my strategy for fear of frying my ECU.