Sounds like a good idea. Since it's happening with all the engines it suggests a user induced condition. Start with the throttle end points and linkage lengths. No binding or over driving allowed. The verify the choke is fully open for every engine run after it has been started. Servo operated chokes could be poorly adjusted and causing a problem. Then go back to tuning basics, starting with both needles at the 1-1/2 turns open position to establish high and low end performance. If those don't fix it try routing that hose to the carb air inlet and see what happens.