Long story short, there's a reason the 5.9 Cummins is so legendary. I had zero issues out of the motor, but I had what I believe was a slowly failing aftermarrket lift pump, and the guts of the NV5600 were starting to go. And the turbo had such a short powerband. That truck only really made power in a 600-700 rpm range. Had to wait for the boost to kick in, pulled hard for a few seconds, then fell on her face and I had to shift. Maybe that was because of inadequate fueling, or possibly a bad wastegate. I dunno. Never dug into that before I got tired of dumping $80-$100 in the tank every week, and spending $120 on an oil change every 5k miles. She was a nice truck overall, besides they stereotypical dash, kidney brusing rough ride, and not a straight panel on her. New headlight housings were my favorite upgrade I made to her. Anzo black housing non smoked, from Summit. They were simply amazing. Actually, favorite upgrade was installing a muffler. MBRP Quietflow. Straight through, absolutely killed the resonance. Still sounded good. Oh, and the most irritating thing was the 4-5 upshift. The NV5600 didn't have a lockout on reverse, so if you weren't careful or got in a hurry, you'd go from 4th to trying to shove it in reverse. Totally frustrating. Another reason I wanted the G-56. Reverse was high left, like the S6-650 behind an 8.1.