Help identifying this pipe please
 

I have a strange fault with the car. The N/S/F drops to the deck when parked so I thought great a strut/compressor/valve block leak however my exhaust is also louder, sounding like it has a leak. Coincidence? Possibly. Checking the car physically and with VCDS there are no faults or leaks. The compressor pumps out 14.5 bar so ruled that out. No hissing and no bubbles with soapy water. The suspension lights come on briefly when started up but the car rises fine and holds perfectly.

I have noticed under the bonnet that there has been a bodged repair to an air pipe, and I have taped it up temporarily. Looking on Etka, I am struggling to find out the part number. Anyone know which one it is?

https://i158.photobucket.com/albums/...pscvjq7bjf.jpg

It looks like the vent hose to me (part number 1)

http://forum.a8parts.co.uk/attachmen...1&d=1572211187

I must be going blind! lol. Thanks steamship.

Any idea of it's specific function?

EDIT: Looks like oil separator to crankcase

That was my thinking as well, and if it feeds back into the air intake (for emission reasons), then I would assume that would be where you could add in an oil catch can.