Mike,
I have a rather radical cam also and vacuum is a problem at times. But when I talked to a Holly Tech. he told me that the gas should just be right at the bottom of the site plugs and that if I take them out it should just barely splash out at idle. My engine idles at 1,000/1,100 RPM. Let me know what you find that cures your braking problem as I still have some but not as bad as before and as I said, I am thinking of putting a small hose on the vents to raise the tops some.
Ernie, did you get yours to stop killing the engine under braking, and if so was it your carb adjustments?
Ron