Has the emissions recall been done on your truck? Also have you tried running the exhaust brake all the time? The worst thing for these trucks, is be-bopping around town. Not an excuse just pointing out that when loaded they do not have any problems. Running on the highway to clean out the soot seems to help also, but this also should not need to be done!
Didn't Ford and GM have the same issue before they went to the DEF based emission system and got away from the EGR system. Trucks that mainly run around empty and driven in town will run a re-gen more often causing poor mileage and can cause the turbo to need to be cleaned?
Don
