1. Exhaust leak - more specifically, one of your bellows has a split in it. That could explain your loss of boost (only 13 psi while you're towing uphill). Get on the driver's side and climb under the truck with a good flashlight and a telescoping mirror. Look for black soot trails or areas where it's "dusted" black.
2. Your drive belt slipping on the water pump pulley when your fan turns on/off. (see @ChrisSki his thread in the link below).
While towing 11k up a grade, my F250 2005 diesel 6.0 Truck Whistles. The whistle seems like its coming from behind the Tachometer. Happens on steep grades, close to 5%, with IPR above 74%, Turbo PSI 22+, but usually 28 PSI. ECT is 215 - 220 and then the fan kicks on and won't go up anymore...
When you’re installing a Bullet Proof Diesel fan clutch adapter on your engine, you might find a glaze has formed on the water pump pulley...
3. Something rubbing inside your turbo. Pull your intake, grab the front of the compressor and check for play. There will always be some side to side (it should never be enough to contact the housing though), but there should never be any in or out (toward/away from you).
There are probably more, but off the top of my head, those are the 3 I would focus on based on your video.
I had a very similar noise when towing my toy hauler up steep grades - I narrowed it down to the EGR valve. I intially thought it was AC related since it cycles on and off, but it made no difference if I had my AC on, so it eliminated that. I had my EGR cooler changed a few months ago, and changed my EGR valve when done, and that seemed to make a big difference. Worked for me anyways.
I got a 2006 F-350 6.0 Diesel with 230k
I actually had the same train of thought with the cycling and the EGR valve. I cleaned it a couple of weeks ago and it, unfortunately, made no difference. Thanks for the help though.
That was some great cross-referencing, thank you. I took the water pump pulley off and scuffed it up. I haven't towed since but I have driven some pretty steep grades and the noise is certainly quieter, if not gone. The real test is when towing. In hindsight I should of put a new belt on there since it's such a PITA to get to it & I think the old belt would be more prone to slipping versus a new belt with the newly scuffed up water pump pulley. Either way, I appreciate you taking the time.
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