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Join Date: Apr 2010
Location: Clinton, MS
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You really need to check for diagnostic trouble codes (DTCs). Throwing parts at a problem is a sure way to lighten your wallet and occupy your time but is not certain to correct your issue. Start your assessment with codes.
Having changed the injectors you could have improperly seated them allowing oil and fuel to bypass the gaskets and/or o-rings causing your smoke. Recent work is frequently a good spot to double check.
There is oil in the turbo on the compressor side because of the positive crankcase ventilation (PCV) system. There will always be oil in the turbo on the compressor side unless you do a crankcase ventilation (CCV) reroute with inline filtration. Your description of the "valve cover going into the intake" is spot on for the PCV system. Oil vapor is picked up along with combustion gasses that blow-by the piston rings from an earlier compression-combustion cycle and recirculated to burn off in a subsequent cycle.
The turboshaft or CHRA (center housing rotating assembly) is oiled of course and if not properly cooled down before shut off, the oil may coke and cause the turbo to seize but this isn't likely to be demonstrated by excessive smoke out the tailpipe. It will throw a code. You won't likely see 22 psi of boost though because it will seize. If it's leaking then you'd see the most smoke under load not with no load as you describe...although anything seems possible with the 6.0L sometimes.
Codes along with a description of your truck's year of manufacture, mileage, your driving habits, and any modifications will further help any "on-board" assessment.
Jonathan D. Howell
Lieutenant Colonel, U.S. Army
2005 EarthRoamer XV-LT (Ford F550)
"Americans Travelling America"