To recap the last week or two of my quest to rid myself of the sudden-open-throttle hesitation:
1. Tried stiffer pump springs. They seemed to help my hesitation but they were so stiff that they overwhelmed the throttle return springs (new ones) and didn't let it drop back to idle.
2. I replaced the pump springs with my old ones but soldered up my bleed back jets. The setup was 40 pumps and 55 bleeds, and was now 4- pumps and zero bleed. It drove better with less hesitation, but it was still there when suddenly going WOT and sometimes when rev-matching.
3. Keith sent me some .53mm pump jets and a drill bit to upsize to .61mm if necessary, as well as some slightly stiffer springs. Holy cow, what a difference!!! The rev-matching and WOT at low rpm hesitation is gone! Once in a while I'll get a short lag in power output because of AFR going lean, but no more bucking-bronco take-offs. Not only that, but my idle is at 14:1 and cruise is 13-13.5:1 (I want this leaner). It feels so much better to drive this car now. My current accel pump setup is stock springs, 53 pumps and zero bleed.
I'm thinking I may need some leaner hypojets to get the cruise AFR where I want it. It's close but I want it leaner, at 14.5:1 or higher. I might as well try the slightly stiffer accel pump springs to see if they eliminate some mixture lag, but I won't want to use them if they mess with the throttles returning. I'd rather upsize the pump jets.
All in all, you can barely tell this thing is carburetted now (especially if you don't look at the AFR meter )!