It is common to see the variable vanes inside the turbo seize or bind from carbon buildup. This causes an overboost or underboost condition when driving.Google+
Car Problem Reports
Ford F-250 Super Duty Variable Vanes Inside Turbo Seize Due to Carbon Buildup
Ford F-250 Super Duty Problem
Engines Affected: 6.0L V8 Diesel Turbo, 7.3L V8 Diesel Turbo
Average Mileage: 92,911 mi (20,000 mi - 166,565 mi)
The vanes on my turbo failed 3 different times. My friend who works at Garrett told me the first time it is due to the small diameter oil return line, Ford laugh at me. Then at 65,000 they told me of their great fix, I laughed after I had them bring my service records and my documented comment.
Visitor, 2006 Ford F-250 Super Duty, 6.0L V8 Diesel Turbo, 105,000 mi
was diagnosed by the dealer.
P2099 trouble code for turbo underboost due to Injector #5 sticking and lack of performance
Visitor, 2005 Ford F-250 Super Duty, 6.0L V8 Diesel Turbo, 166,565 mi
truck makes noise like a jet engine trying to spool up. it doesn't loose rpms but will slow down at higher rpm. does not seem to do this on level sufrace only when pulling any grade. I tow a 5th wheel.
Visitor, 2005 Ford F-250 Super Duty, 7.3L V8 Diesel Turbo, 91,000 mi
this has happened 3 times replaced turbos and is happening again