Need Help With Off-Idle Surge

Well, I finally had a little car time and made some progress, so here's an update:

I monkeyed around with the advance some without getting the result I wanted, then one day when I had time to kill at my desk I decided to call the Holley/Demon tech line. Good thing I had time to kill, because from "1st in queue" to talking to a live person took almost an hour on hold.

The very nice guy I spoke to asked a few questions and said the issue was probably fuel pressure too high, or float level set wrong. I'd been running the basic Carter #4600 7psi pump with the Edelbrock carb for years with no pressure regulator and no problems. Demon says the 625 Street Demon wants 5-6psi, and apparently they mean it.

So I got the Holley 12-803 adjustable 4.5-9 psi regulator and a cheapie Mr. Gasket gauge and re-did some plumbing and finally got to try it yesterday. The good news is the problem went away!

The small bit of bad is either my adjustable regulator doesn't adjust very well, or my gauge is not very accurate, 'cause I can adjust 'till I'm blue in the face and the change in pressure reading is minimal. In any case I have it reading 5-ish psi (the needle bounces a lot), and the engine is happier. The surge is gone and it still runs fine at higher rpms. (I've only had it up to ~4000, but I drive like an old lady anyway.)

I now have a very slight hesitation when accelerating at a little higher rpm (1500-1800) than my old problem, so I'm not done yet, but it is so mild I really could live with it. But it's a hobby, so I'll have to chase this new issue around too : )

I appreciate everyone's advice- Thanks you guys!