I just had the same thing and mine turned out to be a bad cam lifter. The needle bearings on the bottle of the lifter let loose and now the engine will not run at all. some of the needle bearings made there way into the oil pump gears and stopped the oil pump - thus - no oil pressure - no oil pressure to the high pressure oil pump - thus - engine will not run.
My mechanic now tells me that I will need a total re-build to remove all the needle bearings
If your intake is making a puffing sound have it checked out right away.....
I am thinking that I should just drop another 6.0L into the truck, as I can get one for about $2200.00 and total re-build will run over $5000.00
I have turbo farts on mine and power is not the same, even after new injectors, how can I or the mechanic see if that is my problem, my turbo was cleaned at the valves they were not bad, so im thinking I could have this problem.