Thank you Matt,I like your technical and practical approach step by steps ,
Your on target with your first 2 u mention above …
Timing being out will affect your vacuum in the most drastic ways possible so make darn sure u set it to the stainless steel BB per the FSM
And only then final finite adjust via a high quality vacuum guage hooked up directly to your intake manifold
Not the carb base or any other source to be klear here
This the prescribed recipe for sucses
Then once you have dialed the timing and base idle and fast idle also don’t forget …
Transition to the FCS , and confirm and properly diagnose that ..
I have personally had more then one original fcs provide a solid clicking sound a touchy freely click sensation when hand held , yet still be a failed faulty part at the end of the day …
Good luck your on the right path here I feel …
I appreciate the encouragement!
Going back to how the problem started, we were on a short drive and the idle issue surfaced as we neared home.
Keeps me wondering what could have changed in a short amount of time.
I think we'll proceed with another FCS and also an emissions computer since ours has the low voltage issue to the FCS.
We'll also share the vacuum readings (I have good gauge) once the tachometer arrives.