Carb or ignition ?

Checked for leaks and replaced intake gasket with an embosed edelbrock one

Anything out side of that? Power brakes? PCV valve? Possible intake to head angle leak, I know that's grasping at straws and you'd see the oil traces. Its the instability that seems odd, other than possibly a issue with the distributor. Have you tested how strong the spark is? I had a coil go to poop and give a weak blue ark. Possible ECU ground?