Its a one way valve available from the dealer or possibly from GAP or Part4vws.
I need to redo me vacuum lines, and this part decided to be extremely fragile and break... Giving me a constant idle of 1,500-1,600 rpm
It's the part in the middle, with the black hose connecting to the white part. I'll upload a better picture when I can. Also, where can I get this part?
From what I got from my Bentley, it's an intake air distributor... Which just sounds like an intake manifold to me.. So maybe I'm reading something wrong..
That's the brake booster vacuum line, that white thing is a one-way valve. There are usually two vacuum nipples behind the white part, one of them will lead to the A/C vents on factory A/c cars.
Vintage Watercooled Technotes: