[1988 90Q MT]Assembly on driver's side of cyl. head

[James Wagner]

Apologies for making two posts so rapidly, but I have another question.  In
searching for vacuum leaks to cure my idle speed problem, I see an assembly
bolted to the Driver's side of the cylinder head with a manifold vacuum hose
attached.  I can't find a single reference to this "thing" in the Bentley
manual, and it doesn't appear on the vacuum diagrams (unless I'm blind or
stupid - very possible).  I'd like to check it for vacuum leaks, but I don't
dare disconnect it until I know what the consequences are.

Thanks in advance,

Jim

1988 Audi 90 Quattro, 198,000 miles (VIN W.AU.H.C.0.89.4.J.A.235703)