What is the rpm the engine is idling at? Above 1200 or so rpms, the main circuit is coming into play, so adjusting the idle mixture does absolutely nothing. What is the ignition timing set at? Stock will not do in most cases with an aftermarket cam. Do you have specs on this "combination" cam? I could suggest an alternate timing curve perhaps. It could be a vacuum leak elsewhere, have you tried a vacuum gauge on it yet? If you drop below 15" @ idle, the power valve will also fluctuate, and that must be modified for correct idle quality and power progression. Just need a little more input in order for me to correctly diagnose it. Out of curiousity, do you have the higher compression pistons in this engine?
Bob
Bob