Awhile back I had a 2003 6.0l. This thing could tow my horse trailer (8500 pounds loaded) up a pretty steep grade at about 80-85mph stock. I don't know if I was beating the truck that bad because I really only used it too tow and haul things around but I constantly had a turbo problem. You see, almost every time we towed or even driving in general the turbo hose would blow off and I would have to find the nearest dealer to take it in and reattach the hose. Eventually, I went and took it into the dealer and they offered me the choice of doing the lemon law so that we could trade in the truck and get the most current year. So, after I swapped trucks, I ended up with a 2006 6.0l. The first time that I towed with it on the same hill I had to put my foot to the floor and I could only hold 55 mph. So i took it back to the dealer and they looked at it and said nothing was wrong. I went up the same hill again and I could barely hold 55mph. Why is it that I could do 80mph before with my 2003 and now I can barely do 55mph with my 2006?
(Eventually, I went with a tuner and now I can tow it no problem.)