I mounted my cline between the needle and the carb and it works flawlessly. It will work in either location though...

There is one other possibility to your problem though, overheating. Running these motors in a cowled installation can result in overheating and that shows up as a loss of power. Try flying the plane with the cowl off and see what it runs like. If there is a marked change in power, reinstall the cowl and retune the setup. I have noted that all of my cowled engines need a pretty rich setting on the ground to compensate for the higher temps encountered while running under the cowl in flight.