[jhv48]

From the Holley website:
“For high performance engines a carburetor with mechanical secondaries has an inherent advantage over a carburetor with a “controlled” secondary system (air valve or vacuum diaphragm). This is possible because a controlled secondary carburetor, until it reaches wide open throttle, will not have as great a pressure drop below the throttle plates as would a mechani- cal secondary unit. The greater the pressure drop below the throttle plates the more dense will be the fuel/air charge to the engine and, hence, the more output.”

Swap out the carb and be done with it.