Grinding/buzzing noise coming from turbo side of the motor

I have a 2015 frieghtliner cascadia with the dd15 and cannot figure out what is causing this. I am getting spn 102 fmi 18 (low intake pressure) and am 25% derated. I pressure tested the intercooler and hoses no boost leaks there. I have a friend who is head mechanic at frieghtliner I had check the turbo, turbo is good. Replaced all sensors relating to intake. Replaced and had it properly adjusted the wastegate or whatever it is under the turbo. Took it to another frieghtliner dealership and they said it's my head gasket however I have no antifreeze leaks or oil leaks nor am I burning any so how could it be a head gasket? It has 870k miles on it. Im currently driving on it and just did a 5k mile trip other than loss of power and loud grinding/buzzing noise coming from passenger side it runs great? Anyone got any ideas? It's driving me nuts that frieghtliner mechanics and other mechanics can't figure this issue out. Thanks

 

Wouldn't it have flown apart after 5k miles of driving? I'm otw hom now from a short 800 mile rn and it's buzzing just as bad as it was last week. In my Duramax when the turbo went out it was a matter of miles before it was completely toast lol

 

Alright thanks for the tip I'll take it to another guy and have it checked out when I get home in 2 hours