I've bought a used VW/Audi recirv valve, part number 034 145 710 C which I believe is reasonably commonly used with G40 turbo conversions. It's the same as in the photo below pinched from an American Audi site.
The valve doesn't appear to operate as I would expect, but would like to make sure I'm not misunderstanding the valve before condemning it...
If I suck on the vacuum line then it will suck air through the 'pressurized air dump in'. When connecting the valve to a vacuum line on my engine it won't open, but when the valve is gently pushed open through 'pressurized air dump out' the vacuum will hold the valve open.
I suspect the diaphram between the vacuum side and the boost side of the valve is shot, but looking for confirmation please chaps. Cheers.