My '08 6.4L engine is all stock. Its a part time vehicle and only gets used about 6000 miles a yr, half towing and half running around town. During the 3000 miles of running around town (not towing) it almost never goes into "cleaning exhaust filter" mode. During the 3000 miles of towing my 5th wheel toy hauler, it goes into "cleaning exhaust filter" mode about every 200 miles and the cleaning lasts about 10-15 miles/minutes on avg.
Shortly after I bought this truck (used 2 yrs old) it was constantly going into cleaning exhaust mode and running very rough. The dealer found a sticking EGR valve and after changing that its run perfect ever since.
