Ur-q mystery valve

["Rod L. Wiggins" <rwiggins@rs6000.baldwinw.edu>]

 Greetings all, 
  I am hoping there is someone out there that can help me identify a 
mystery valve on my car, I can seem to figure out what it is and why its 
there, I only know the car is much happier without it.

   I had a rather elusive High idle problem that I finally solved. 
However , I has raised a very intriguing question as I can not figure out 
what the purpose of the faulty part was...  When the car was warm it 
would idle at 1600-1700 rpms. It would slowly fall back to normal. Slow 
enough that it would not reach normal levels while sitting at a stop 
light, but fast enough that things would return to normal before I could 
locate the problem. Well I finally found it!  There is a valve back near 
the frequency valve and auxilary air regulator that allows metered air to 
bypass the throttle plate and subsequenlty raise the idle. the valve is 
actuated by vacuum. Apparently opening when there is vacuum fed to it  
. My valve was opening intermittently resulting in my high idle. I 
eliminated the valve and the idle problem is fixed, the car seems to 
start better and the part throttle response seems better (probably my 
imagination).
  My question is, What is the purpose of this valve?  What is its 
intended function? Is this Audi's early attempt at bypass valve?


 The valve is a cylinder about 2" long and 1" in diameter. there are 
three inlets, one small for engine vacuum and two larger (3/8" or 1/2") 
that are connected one to the bottom rear of the intake manifold and the 
other to the same tee that feeds metered air to such things as the 
auxilary air regulator and the air conditioning idle-increase-solenoid 
(or whatever they call it).

I'm ashamed to not know what a part on my car is there for...
But if it doesn't make the car go faster, I guess don't need it anyway.

Thanks in advance,
Rod
83 Ur-quattro