I'm confused by your description of running rich on the ground. With the Emas carb the high speed needle has an effect in the midrange as well, hence my comment on the overlap effects of the mixture needle adjustments. Depnding on the application and installation you could be experiencing a pressurization of the metering diaphragm but I've never seen this be an issue with this carb, mine has the metering diaphragm cover facing forward and gets the prop wash full force on the cover.