318 carb issues

Old thread but the problem is still here after a new timing chain (old one slipped shortly after this), and new fuel pump. Air/fuel screws are set at 1 1/2 turns out, that seems to be where it likes. Same issue, no issues in neutral, but big flat spot under load around 1/2 throttle. Different ignition as well, lean burn was swapped in favor of a non digital msd 6al