Surging at low speeds and not at high speeds definitely sounds like
either a vacuum problem or maybe a throttle butterfly problem (which
turns out to be a vacuum problem). Did you check to make sure that
your throttle butterflies are tight and closing right? Maybe your
throttle shafts are worn allowing air leakage, which screws things up
at idle but makes no diff at full throttle....
If you have secondary butterflies (cast arn dual manifold) you could
be having a problem with them also, a loose screw (we ALL have them!)
(Para los que hablan español, se nos aflojó un tornillo....)
or some such. I had a loose throttle butterfly in my 164 and it took
me MONTHS to figure it out!

If your engine wouldn't idle with the hoses hooked up backwards, you
know which way is backwards! You also know that you have the fitting
with the big hole rather than the metering jet fitting I have in my 164.
(which I have drilled out bigger on a couple of occasions but it is still
not big enough to pull in all the blowby!)
--
George Downs Bartlesville, Oklahoma