One of the problem with the 6 leaker is the variable vane turbo. If you don't run the shite out of that motor and get the EGTs up high enough to cook the soot out of it, the vanes soot up and frick the turbo all up, leading you to a nice new turbo purchase.
The high pressure oil pump and EGR valve are really the only two things you need to look out for if you take care of them well.
ETA: The 6 liter was designed to be a hard-run engine. The people I know who've had good luck with them pull heavy and often with them.
The people who've had theirs in the shop more than on the road sat it in traffic a whole lot.
This post was edited on 11/18 at 9:34 pm