Try flow testing the system through the carb. bowls instead of directly out of the fuel lines. When I replaced the Magnfuel 275 pump with the Magnafuel 300 pump it flowed the same amount with the fuel lines(six pak, three lines) disconnected I called Magnafuel and they said that I was NOT testing the pump correctly, to restrict the flow with the same size as the needles and seat. I hooked up one fuel line and the fuel flow doubled