Check the airbox rubbers to the carbs and make sure they are secure and have not popped off due to overtightening of the clamps. Never torque them tight like an ordinary hose clamp or you will not get a proper seal. You could also check for a vacum leak from the 2 sources above the carbs where you would tap in to source a Scott Oiler or a previous vacum fuel pump. Choke plungers working correctly? You have 12 volts at the pump I'm assuming when it's running?