I have same bars on my 2019 F60All4S, but no whistle. I will say that I feel like our cars are really loud when it comes to wind noise in general so who knows what is causing your whistle. Do you have the little ribbed rubber strip that slides into the top of the bars to direct airflow?

 

Do you have a sunroof? There was not a whistle before install so it's definitely the bars. I have the rubber strip installed and the end caps are installed properly so that there's no gaps on the edges. Not sure what else I could do. They're installed exactly the same as my other car that doesn't have any whistle issues. Kind of weird.

 

Any chance you could swap just the bar portion over to your Mini? If so, you could determine if there is something about the bars themselves...

 

I thought about that but her front one is a different size and too large. When the weather gets nicer I may try swapping with the rear bar and see if there is any change.

 

This is EXACTLY what I want to do, but I don't know what bars + feet, box, and ski / board carrier to get.