gwcrim,
Just a few thoughts. The colder temps should be making your bike idle higher if anything. If you've exhausted all other adjustments, check for wear on the idle screw, also a leaner pilot jet would give you a higher idle. My recommend Airscrew setting is from .5 to 2 turns out. It is a fine tuner for the pilot jet and kinda subtle. I use it to get rid of the lean surge when it starts to get colder out. Once I'm turned in to .5, I go to a bigger pilot jet. With a little experimentation you should get the results you want.
Joe Chief