Originally Posted by Brian Bosley

This sounds too consistent to be an air leak but I wanted to recommend that you don't tighten the screw that holds the linkage on to the barrel of the carb too tightly because you can crush the barrel and not even realize it is not sealing properly. This can easily be identified by the carb boot being wet. You may need an o-ring kit for the carb as well if the needles are too easy to twist or appear wet.