BIL's 09 6.7 cummins had the constant CEL with the continuous trips to the dealer because of the emissions system and all they would do is clean out the emission system, tell him to drive with the exhaust brake on, run a fuel additive and send him down the road. After 9 months of the run around he sold that truck because the dealer couldn't provide any real solutions to the root cause. I suppose the class actions took care of these type of impacted customers. The only people who didn't exhibit these problems were the ones who towed heavy on a frequent basis.
His 04 and my 05 6.0 PSD also sooted up the EGR valves and would require cleaning every ~80k miles.