Occasional tinny rattle through vents

[Darcyvrs]

Hello all .. got a strange issue I can’t figure out .. here goes ..

 

octavia 2008 estate vrs cr tdi 

 

it has a rattle at 2000rpm . Sounds like a tingle or very high pitched rattle . Sounds like it’s coming through the air vents . Put the fan system into recirc mode makes almost the same sound . 

Is there a common problem with a flap or something ?? I’m struggling . 

 

It it has had a new clutch , flywheel etc etc within the last couple of weeks before anyone suggests that lol ..

 

any help or micky taking gladly appreciated.

[Darcyvrs]

Ok after another look I believe it’s definitely something to do with the recirc on the ventilation system . 

 

Is is this a common easy fix ??