co2 is not combustable. in fact they used to use that in fire extinguishers. (can't anymore due to air quality blah blah in CA).

so adding a stream of co2 to the intake a good idea? I doubt it.

while the intake temp might go down a bit by the time it reaches the cylinders the effect would be minimal if any. also you're mixing co2 to the intake air... which does not combust... bad idea.