Mystery valve in engine ... snapped

[Jeff GTi]

I have been re fitting my jr air filter after giving it a good clean and noticed that at the top of the TIP near to the maf, there is a small grey and black vacuum valve, well mine is snapped and was free floating

I have managed to remove the piece lodged in the TIP and the valve itsself now but I'm wondering what it is, what it does and is it a common failure part, will VW carry these as I need my car daily so need one asap

[kc]

can you get a picture buddy?

ill have a check!