High pitched whistle

What could be causing a high pitched whistle when I first press down on the gas after shifting gears?

Does whistler have a carburetor? Maybe its loose and the throttle cable pulls it away from the manifold and the air being drawn in the gap whistles.Really why do you think its better if you don’t divulge the make,model,year of the car?

Okay, the whistler is a 2001 BMW Z3 Coupe. Sorry, Im new to this.

Good its a BMW,I cant think of what it could be but my friend is a Master Tech at BMW I will E-mail him,post back latter tonight or tomorrow. Air pump for emissions is my Wild A** Guess we call this a WAG

Have your mechanic check adaptation values,these could indicate vacuum leak or bad crankcase vent valve

Have a 2002 Mazda MPV that whistled, although it was more continuous. It was a PCV hose that is too close to the EGR pipe and had so melted through (actually melted onto the EGR pipe). Your whistle might be a loose/damaged hose somewhere as oldschool suggests.