That sub zero temp makes jetting even more difficult. The motor's packing more punch with that cold dense air. The fuel is more dense too. You have to run a richer setup because of it. Your WOT sounds about right, though you may need to go to the next richer needle if your clip is already at the bottom.
Needles are cheap.
When you get the new one put the clip in the middle position and try it out. Running too lean here can make a motor sluggish. It seems like you're getting very close to where you want to be. Rick Back to The Thread Spread index of articles.