Problem with Holley 4 bbl

Do you have an idle circuit on the secondaries? 4 mixtures screws? If not then that’s a bad sign, no wonder the mixture screws do nothing, and it’s rich. You just identified a BIG problem. Yes in your first post you tell us “excess gas is entering the system” You just nailed it. At idle the fuel needs to go through the idle circuit for the mixture screws to do anything. You are bypassing the idle circuit.

If your plugs are fouled again you will need new ones again.

What is you idle vacuum and what power valve? It will add fuel all the time if it’s the wrong one.

There are many unanswered questions here.