Have high pitch whistle coming from intake manifold. Any comments?

 

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IAC Valve has a Black cap over a vent, and it can make that noise if IAC Valve is leaking a bit

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The Vent allows the valve to move in and out in the cylinder without air pressure building up behind it, it equalizes pressure, so not suppose to suck air in, but if valve leaks a bit it can make a whistling noise
The cap pops off and you can put your finger over the vent while engine is running, if whistling stops you found the source of the noise.


Other sources could be a small vacuum leak, but very hard to find these.
Smaller diameter rubber hose, like vacuum hose size, can be used as stethoscope to listen at gaskets


High pitch "noise" on the 3.0l can also be the Cam Synchronizer, by firewall, Cam sensor sits on it, it's bushings wear out which causes a high pitch noise but usually described as squealing noise