I have this whine and I'm trying to diagnoise the problem, its only on cold starts. Sounds like air flowing across a partially closed valve.

I was looking at the airbox and at the bottom there is a vacumm operated valve (flap type) about 2" in diameter. It is naturally in the open position and when the car is turned on it closes. The routing of the vacumm lines goes across the passenger fuel rail to a vacumm module under the 4.2 trim piece. The intake line goes under the headlight where it disappears.

Does anyone know what this is for and if it is needed?

 

I checked online and the only thing I saw this called was a front snorkel from an aftermarket intake assembly. They capped off the vacumm line to this item.

 

not sure if your car has a secondary air injection pump, but mine makes noise for about a minute on a cold start. If the car has been driven and is warm it won't do it. Only does it first thing in the morning, or when I leave work if I don't drive it around at lunch time.