Clean and properly gapped spark plugs and spark plug wires are essential for making good hot sparks. I'll agree with you that when its -10 degrees your engine needs all the help it can get.
clean fuel injectors are also very important to atomize the fuel to coax it into evaporating when its that cold.
My suggestion, change the spark plugs and wires and add a bottle of fuel injector cleaner at the next fill up. You may even want to try adding a bottle of dry gas on a regular basis too.
Alot of people say good things about injector cleaners such as Chevron's Techron, or Gumout's Regain.
