I have a 2008 F350 5.4. I have blocked the cam phasers, new chains and tensioners, new rollers. I did this as the engine would not run and I found major damage from a failed cam phaser and chain system. After the change out I did not like the repeated failures and had the phasers blocked with a ECM reprogram to prevent codes and adjust set timing. A squeal or whistle started up after this work was done. First thought was belt. I changed out the serpentine belt, idler, and tensioner pulley. The squeal / whistle is still there so I removed the belt completely and ran it. Problem still there so it is not to do with anything belt driven. I have read about the PCV routing and testing causing a whistle. If I pull the small hose off the passenger valve cover nothing changes and I feel no air pressure or vacuum. Same with removing oil fill cap. On the drivers side the large PCV hose when removed the enging wants to die and there is a large amount of air/vacuum coming from the hose. In the photos I included here it says the PCV is stuck wide open. Other threads say the PCV is not a valve like most engines but it is included in the valve cover. I am not sure what to think now. Some find the noise comes from the dipstick tube. I do hear the noise from the passenger side.

I was afraid to drive it before, but now I am more convinced it is a minor issue and not a bad bearing or valve train issue. Still I need to figure this out. Another thought discussed is bad exhaust studs or a leaking exhaust gasket. I cannot find any leaks with my hands around the manifolds. I am not sure of any other way to look for the leaks. The mechanic I use when I cannot fix things has 2nd degree burns from a customers truck blowing a hose while he was under the truck. It may be a few weeks for those big burns to heal. Twice a week he has to have them scraped and redressed. Looks real painful. I do not think it is the exhaust leaking because it sounds more like a whistle. The best I can describe the sound is a bad intercooler boot or clamp on a high boost turbo.

 

Maybe a leaking broken vacuum line that got damaged performing the other work, or one wasn't reconnected.