Why does my Audi A4 have a high-pitched whistling noise while accelerating?

I recently noticed a high-pitched whistling noise while accelerating in my Audi A4. It seems to get louder as I press down on the gas pedal. What could be causing this and how can I fix it?

The most likely cause of the whistling noise is a leak in the vacuum hoses. Check for any cracks or loose connections and replace as needed.

If the noise is coming from the engine, it could indicate a problem with the turbocharger. Have a mechanic inspect and potentially replace the turbocharger if necessary.