^ def agree with moving the needle clip. in addition to that, have you played around with the air mixture screw at all? start with a 20 idle and 180 main, and do a half turn out and see if there's any improvement. if there is, that may be your culprit, and you can dial it from there using quarter turns. if not, i'm guessing air leak of some kind, (though probably not the bottom end) or your carb internals (float or slide) are stuck somewhere.