Malc, you could set up a purge style switch for cooling while sitting still, and not have it pedal activated. Im sure it could be set up however you'd want. The only thing Im unsure of is if you could spray up. While moving down the road, the air flow thru the IC might not allow the spray to go upward. But if you went downward, would the supercooling make it as far as the exhaust manifolds? cause you definitely don't want to cool those down or even worse have liquid CO2 land on the manifolds.
On the plus side, how would it be to have 30-40 degree intercoolers on an 80 degree day?!?!
As far as the cost goes, Ive read CO2 is about $1.50 less/lb than Nitrous