What could cause intermittent boost lose?

[Hooper]

My neighbor has an 05 F250 6.0L auto and is on a trip with his 26' trailer. He called me with an intermittent boost lose when he has his foot in it going up a hill. When he doesn't have his foot in it, everything appears to be fine. It's not blowing black smoke either. He pulled to the shoulder, say's boots still attached to cooler tubes and cooler. Didn't hear anything under the hood out of the ordinary, but when the boost failed, he did hear a slight whistle. He's dreading the drive home (5hrs at normal highway speeds) in this condition. Any thoughts would be appreciated.

 

[f100cleveland]

I'd say he has a turbo that is sticking and not letting the vanes move. Some additive to help clean the build up for now and then drive it like he stole it to exercise the vanes might help. Then when he gets home a turbo off cleaning. I had issues like that at least 3 times before egr delete. I also added a road draft tube for crankcase vent so oil vapors don't go through turbo.