Fuel pressure is critical with the Weber’s. Not so much with the pinto 5200. The Weber’s need a steady 3 pounds or so of pressure. If using a mechanical pump, the pulsing prevents a steady pressure. I am not saying that is the issue, but it’s certainly in the mix. As to flow, I have the same calculations as you and while theoretically they should be large enough, in practice, I still think they are a little too small and a lot of people who have run that carb at higher rpm and mph like you are have had the same issue.
