High pitched noise under acceleration

[sam9green1]

Hi all

I've noticed a high pitched noise while driving my 17 plate T6

The noise only comes when accelerating and is relatively quiet but it's definitely there. My first thought was a boost leak but would have expected a loss in power which I don't have.

Any ideas?

Thanks

 

[Kind of Blue]

Cat in the engine bay? Some one will have a better idea I am sure.