HEI Problem or AC Problem?

[treefrog]

I converted to HEI, timing was right it seemed. The same weekend, I changed to a POA valve update kit, keeping the R 12.
The AC is fine, The HEI seems fine. BUT, there is a hesitation on the highway approximately every 7 - 10 seconds, when I'm running with the ac on, that is not there with the ac off. I am slowly turning this truck from a really neat driver into an ulcer. What did I do this time? Any help would be appreciated. TF