“Whistle” noise from engine when engaging WOT

[Matin]

Hi All

Hope everyone is well.

I’ve recently developed a symptom on my 500E, when I engage WOT / kickdown, I get a “whistle” type noise from the engine.

I’m not sure where the noise is coming from exactly - it doesn’t happen when you just rev the engine normally, it always happens when WOT / kick down is engaged.

Has anyone experienced this before? Anyone have any ideas?

My first thoughts are it may be some of the lines connected to the MAF? Could this also be belt related?

Thanks!