Re: annular discharge
some of this might help.
i had a brand new 650 vac secondary holley on a modified clev a few years ago.i got annullar discharge boosters put on the primary side.they make a 650 cfm sort of like a 590 cfm as they are bigger than the original booster,so ultimate flow is less(because there is a bigger item in the way,).but responsiveness at all revs is much sharpe,the signal is stronger.they are well worth it,i guess these days you can get holleys with them standard,dont know.
i got mine fitted by high flow indution techniques,i think they are still around i was getting them to flow the carb and set it all up just right so got them to fit the annular boosters.
(i would reccomend h.i.t for any work for those in w.a,they explained patiently any questions i had about this stuff)
as for four corner idling i have no experience with it but im guessing you have idle adjustment on all four venturi,instead of just the primarys,but im just guessing,