Its a buddy of mine. It is a plumbing service truck. It has a TS 6 pos. chip Banks elbow & exhaust & gauges. One of his workers took it about 60 miles pulling a bobcat. Went where he was going & about half way back he stopped for lunch. He says when he started it back up it ran kinda rough & smoked a bit, smoothed right out & he headed home, he looks in the mirror & there is this trail of smoke!!! Truck runs the same, no noises, no missfire, fluids are good, nothing in the fluids. It was set on 50 HP & this truck is a 235 factory. The workers don't know where the switch is & they have been told to never let the egts get above 1200, there is road construction where he was going so it couldn't have been at 1200 or above for very long anyway. any ideas? Old diesel guy says its an injector stuck open but it still runs great. Has about 130K miles, has never had any injectors. Rocker covers have never been off for that matter. Oh & if it helps it has had a real rough idle in the AM when cold for about 1 minute for the last couple years. Chip & etc has only been on for about 4 months. Thanks!