Considering the cooling effect, have you ever had a look at the stuff from CRY O2 (
http://www.designengineering.com/)?
They make cooling systems for intercoolers and intakes. The idea is NOT to chemically change the air fed into the motor, but just to dramatically reduce the temps, making the intake air denser. I know my car has a bit more get-up-and-go during the winter. Cooler intake air, combined with a 160 degree thermostat to keep coolant temps down and ignition timing advanced could allow the engine to stay in its peak power producing zone.
Thoughts???