My truck seems noticably quicker in cooler weather now. My truck is a 05 Roush intercooled screw.

 

Like every motor out there, the cooler the motor is the better it'll run, unless your just warming it up. Alot of top drag teams will actually even keep there gas in a refrigerator so that the car will run cooler and give off better times from what I hear.

 

Colder air is denser. Denser air has more explosive potential. Colder denser air leads to more advanced timing and spark. Yes, it will run a helluva lot better in the cold

 

Im in NY, I actually get 1 more lb of boost when its colder out.