Ok so my car has been making this noise first of all for about 6-8 months. There has been no negative side effects what so ever from it other then it feels a bit sluggish.

I don't think it's a pulley noise because the whistling is constant when the engine is running faintly until I unscrew the oil cap then the whistling stops. The Noise gets louder when I shut off the engine and then makes a high pitch noise until it's off almost like a tea kettle boiling.

I think it's a vacuum leak somewhere but I have looked everywhere and can't find it. I even removed my intake manifold and replaced the upper intake manifold gasket.

Turn up your sound it's a bit hard to hear...

 

Sounds like the ABS pump.

 

But does that explain the vacuum issue with the oil cap?

I'll try unplugging it and turning off the car with it unplugged.