My Nissan Maxima makes a whistling noise when I accelerate. It is quiet when idling. It runs fine. What is making that noise?

have vehicle scanned for any trouble codes

Clean or replace EGR.

If it's not your rotors and you've had it checked out already (because you always want to start with the cheapest option first), then it's probably going to be your bearings. One other check you can do is on your control arm ball joints. If they're shot, it'll make noise and when you take the weight off of it, the noise will go away. You can spray some silicone lube and test drive it to see if it quiets the noise if that's the problem though.

Unplug the IAC. Does the noise go away? If so you probably have a bad PCM (computer) and IAC. Possibly bad wiring to IAC. IF noise does not go away unplug starter, does noise go away?

check for a cracked manifold or cracked flex section at the manifold
it is under load so it is not a vacuum leak as the vacuum is low under acceleration and high under deceleration or idle
indicates a gas leak or possible blockage from failed cat converter

check for a manifold gasket / pipe leak

change the air flow meter

It may be throttle position sensor or camshaft sensor. Most likely the throttle sensor.

sounds like the door/ window seal is broken open doors inspect rubber molding all around the doors/ windows good luck later

maybe is the air compresor and that's the noise that you hearing. Put the air in off if the noise stop, your problem is the compresor.