scratching my head ? engine stumbling

[roadking]

my engine acts like its almost running on 7 cylinders kinda out of the blue, 2000 miles on a gm crate with new everything. eldeblock 600 carb., edel fuel pump and intake, summit hei. engine was running fine, last thing i did to the engine was adjust the idle mixture srews, ran fine after that until i started one morning about a week later then it had the miss. heres what i"ve done since then. had ignition module checked, changed plugs. wire , cap, rotor, checked voltage to the hei, fuel filter clean, adjusted ims about 3 turns out, choke opens up properly, timing has not changed (10degree) seems to be getting plenty of fuel, engine is not smoking. i have not done a compession check but doesn't seem cylinder related. so im kinda scratching my head now, is there anything else i've i need to check? thanks