A4 1.8t noise near airbox

[chuddly71]

I have a 2004 A4 1.8t which has developed a strange noise, that I have not noticed before. It seems worse around the air box. I have uploaded a video to youtube so you can hear it. I have no fault codes on the car. The noise does not change when the car is under load and does not change if the clutch is pressed. I have had a good search around and haven't found another 1.8t that sounds anything like it. The noise for a second or so after the engine is turned off.

Any help will be greatly appreciated.

A4 1.8t noise - YouTube (https://www.youtube.com/watch?v=HirJAxHazSI)

[FrenchAudi]

Just an idea - Alternator freewheel pulley or bearings?