re. gutted cat for dinner

[Swann, Benjamin R. (BSWANN)]

[So, for fuh-evuh I've had an un-diagnosable, intermittant high idle problem

on my '87 5kcstq. Many an audi wrench couldn't figure it out.

Latest guy is thinking bad cat. It does make a tinny-vibration noise 
sometimes (I assumed it was just a bad hanger or something). It kinda makes 
sense; bad cat sends bad info to O2, the confusion begins.]

I don't believe the "clogged cat" theory!  IMHO, you should stick with one
good mechanic who will troubleshoot and see the problem through.

Have you checked to make sure you are getting voltage to the throttle
switch?
Center Pin I think - double check Bently Wiring diagram.

[History: new isv, throttle switch, tune up, coolant temp sensor...and much 
much more!]