Welcome to the forums.
Could you give us a bit more information, what does the whistle sound like? A pressurised air sound which might indicate a vacuum leak, or a bearing whine?
Have you tried to locate where it is coming from? If you move your head around the engine bay with the bonnet open you can get a pretty good idea of roughly where it is, with that information we can get a better idea of how to guide you.
If you can grab you phone and post a short video of the engine bay with the engine running that can help.
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