Misfire at cruise, popping/afterfire at 3000RPM

I have verified the front outboard is opening, but the rear is sticky. I temporarily disconnected the rear, so I’m just running on the center and front. I would think with essentially a 4 barrel I would be getting enough fuel, right?

One thing I plan to do while the transmission is out is change out the tank to pump line for a 3/8”. From what I understand the 440 six pack should have a 3/8” and not 5/16” line, which is what I have.