I had similar problems with my Evo motor that came with my Alpha. During the summer she flew fine without much adjustment but once the temps got below 30 degree's F it needed to be a little rich to run. Adjust the high speed needle a few clicks counter clockwise and it should take care of the problem.... atleast it did for me.

As for flying in the cold well.... it usually has a lot to do with your tolerance... i draw a line when my thumbs/fingers get too numb.