While I admittedly have very limited experience with the NOVI-2000 superchargers, I would suspect the main reason lies behind how much more dense air becomes at those temparatures and how this will adversely affect the AFR. Even though the intake charge is much cooler, this is offset by the extreme density of the air, compounded by the Vipers "goofy" stock AFR calculator that actually pulls fuel at low temps. What you end up with is a lean condition that can also result in detonation. Fuel cools the combustion chamber during the compression stroke by continuing to evaporate, which is endothermic, or "takes heat" to complete. When you have less fuel, and more air being compressed, the amount of heat produced from the compression increases, moreso than the offset of cool air being inducted. Detonation can be your enemy...both at high temps, and low.