Sorry for repeating myself. I'm the type that goes nuts if they can't understand a problem and solve it.
No apologies necessary. In fact it is refreshing to talk to someone that really wants to understand. I, too, want to understand more than I do, which is why this thread is of interest to me. I am by no means
and expert. I learn by trying and talking to others more knowledgable and by reading.
If I were you, I would first do some diagnosing. Have you hooked up a vacuum gauge to your idling engine? I can tell you a lot. Read these:
And From an ASE Study Guide
There was one really amazing page that I'm still looking for...
A simple vacuum test could reveal a wealth of info that you had no idea about. I'm assuming of course that you have a vacuum gauge. You may be able to rent or borrow one from a big box auto parts store for little to no $$$. Worth a try and it could definitively reveal issues for you.
After this initial test to see where you're at, the next thing I would do is to reset everything on your engine to factory specs (or if modified, recommended manufacturers' settings.) That means timing set back to factory, then idle, then idle mixture, then idle again. Recheck timing and test drive. If all feels good, then switch to your new manifold vac setup and do it all over again. At the very least, you're learning to live with/work on your engine. My Chevelle and El Camino are basically stock, so a baseline reset is easy for me to reproduce. I'm not sure what happens with "other" carbs/cams/distributors are introduced to the mix.
I hope this helps you at least get started. I'm sorry I'm not a more authoritative knowledge base for you. I would love to know how you do.