Two of 3/16 holes is a mighty big idle air bypass.That works out to .055 in sq. Thats the equivalent of a .265 round hole! You wont find that much bypass air in the pcv, unless you gut it. However, IMO, I still recommend you run one.
And Im still interested in plugging the PV circuit during the idle tuning.I hate having to tune twice.
I havent worked on anything near as nasty as your engine. I wonder if your combo might be one of those that could benefit from using manifold vacuum on the vacuum advance can. You could still have the same 24* initial, but as soon as the engine runs, it could pull in another 8* to12* or so.These degrees would drop out as manifold vacuum drops out with increasing throttle. And the 36* degrees of total idle timing, might just be the answer. I guess the hard part would be getting the v-can to activate at the relatively low idle vacuum, yet drop out when its supposed to.
I feel the Dcr on your combo is wanting more idle timing.
I think MSD makes a neat dizzy with selectable electronic curves,including a start-retard,and a vacuum curve, that might also be of interest.
With the higher idle timing, the engine might be much happier.I guess it would be easy enough to prove, before buying parts.Just crank some more timing in and see what happens.You may be able to reduce the curb idle and/or secondary cracking screws, to the point that the mixture screws begin to function correctly.
Or maybe you have already tried that?