Chasing a whistle sound from 2005 6.0

[nsogiba]

Hi all, I'm chasing a mystery whistle sound on my 2005 Suburban 2500 with a 6.0. This is not my video but it sounds exactly like this:

The truck is stock except for a cheap CAI.

I have already done the following and the noise still persists:

Checked intake snorkel for any air leaks at couplers
Removed CAI and ran engine with MAF unplugged
Replaced Intake manifold gaskets as well as valley cover gaskets
Cleaned driver's side valve cover PCV orifice (fixed orifice style) and replace PCV hoses. No blockages or buildup

As you can see in the video the whistle happens at various RPMs and seems to come from different locations, and mostly does it when it's cold out. It sounds like an air leak but I think I've ruled that out. Some folks on the video comments mentioned the A/C tensioner being the cause - I did replace mine a few thousand miles ago wtih a Gates 38159 A/C tensioner. Next steps are to run the engine with the belts off and see if that helps.

Anyone ever seen this before?

 

[Scottydoggs]

take the oil fill cap off see if its gone, if it is, the pcv valve is clogged solid and the noise is the engine actually sucking air in past the front crank seal.

 

[OR VietVet]

Yes, take the oil cap off. I agree with @Scottydoggs. But I am also hearing that screech noise that is likely belt or some pulley bearing related. Once the whistle noise stops, in the video, I can hear the noise I am talking about.

What does it look like under that oil cap and down the oil fill tube?