Everything I'm reading says the vacuum keeps the rods down at idle. And generally speaking their thinking you have the same vacuum at a steady cruise at low RPM. When I check my charge for my Edelbrock so I use the yellow spring. But again remember they had bigger primary so they weren't trying to suck it from such a small hole like these smaller Street demon primaries. So I feel I'm getting more vacuum with these carburetors.I've been trying to jet down enough to not have to turn the idle mixture screws in past 1 and 1/2 turns but again like my Edelbrocks in near 3/4 of the turn to 1 and 1/4 turn. And I'm at about 1 turn to 1 and 1/4 on all of my idle screws. the first thing I'm going to do is get it warmed up and take it for a short drive tomorrow and then just start putting fatter or stronger Springs in and see what happens now that I seem to have this idle and everything else under control. Also I do have those 31 squirters up top and I can put stronger squirters in as well to see if that helps again.
One more thing I have is those metering rods coming the 58/44 s and 58/50 s...
Again that article States putting richer rods in the front carburetor...