Idle Issues

[Tom Egbert]

Actually the latest version of the same valve that is being sold today
spec'd for the TT, A4, etc. is considered to be more durable and
 better.  I
believe the last 4 characters in the p/n are 710N instead of a much
 earlier
letter as indicated by etka for our cars.   I put one in my Avant when
 I was
chasing a different type of problem.  

  
   710 is fine for stock application only. If you tell the dealer it is for the '91, they will charge you 10 more dollars for the same part. 
       More boost changes characteristics of recirculation. With even 15 #s you will hear the valve open alot. If you ease into the throttle, let off and then hit half way, the car will hesitate. The diaphram will only last 12 months tops.
     If you go to an aluminum valve you can tune with the appropriate spring for the boost level. On most forums you can find that people put the forge valves in backwards to keep from premature opening. Sounds different though. Just fun to play around with cause it is an easy change.