Why does my Audi A3 make a loud whistling noise while accelerating?

I've noticed that my Audi A3 makes a high-pitched whistling noise when I accelerate above 30 mph. What could be causing this and is it something I should be concerned about?

The most likely cause of this whistling noise is a leak in the vacuum system. It may be a small and easily fixable issue, but it's still recommended to get it checked out by a mechanic to ensure it doesn't cause any further problems.

If you've recently modified your exhaust or added a performance air intake, that could also be a potential cause of the whistling noise. Make sure all the modifications are properly installed and consider going back to the stock parts if needed.

Another potential cause could be a faulty turbocharger. If you notice a decrease in performance or any other unusual symptoms, it's best to take your car to a mechanic for a proper diagnosis and repair.