I have been extremely patient with my local dealer about my early model 07.5 6.7L. My fuel mileage has not been what I think it should be. My re-gens have not been what I think they should be. There have been a continuation of small things thru the last year and a half. I added a bypass filter 4000 miles ago and wanted to wait till I got results back on Blackstone before I took the truck in to the dealer. They now have a diesel man that is extremely well versed and we talked for an hour to give him my truck’s background. The codes my ECM is throwing are few and nothing like I have seen others post here. The diesel man talked to Cummins direct and they have done the following and I just picked the truck up and drove it home. Time will tell. He replaced the entire EGR system. Re-flashed with “AZ”. Performed the last recall for firewall cover for EGR. The drilled and tapped and cleaned turbo. He reset every timer and log in the computer. I had 2.5% fuel in oil per Blackstone test. Cummins indicated they were not worried till fuel mixture reached 7%. Teck also indicated that the engine computer has a memory that remembers how you drive and the load you put on engine. Cummins suggested to not idle your engine while you were disconnecting your RV. He said after your RV trip and your overhead was showing your mileage at 8-9mph, it may take at least 30 starts and restarts and trips to reset the system before you would see better mileage.