Update to this issue:
The idle surge is only present when the engine is cold.
As soon as the engine warms up (160F or greater) the idle is perfect.
Timing is verified via drip method dead on 24 degrees, also tried slightly advanced and retarded, made no difference.
Replaced rack damper - tried several points of adjustment. All the way out I can get it to surge at all engine temps. After engine is warm, I adjusted it in just until the idle smoothed.
I have both a newly rebuilt lift pump plus an electric lift pump / filter at the tank.
Overflow spring in IP is new (slightly stiffer spring)
I do not have a cigar hose, but I have tried without any hose at all and no change.
As mentioned, once the engine get some heat into to it runs fine! I have done plenty of searching but haven't run across this issue before