x2 on the fuel filter and check fuel pump too although just about anything should be enough flow at idle.
Assembling the main jet tower on that Roch. B is tricky, the gasket has to seal and everything has to be aligned just right or the power valve needle can stick open or shut. Maybe the wrong ball is in the power valve recess(too big)? Any misalignment could force a vac leak between the tower and the carb top, and this is where all the fuel flows up from the main jet so if there is a leak there, the carb would misbehave all over, much as you describe. I'd bet on that as the leak point.
