Superchow,
You would be a good scientist, I am not sure about you making a good engineer
Your answers are summed up by roflwaffle and jamesqf. Christ has taken care of demolishing the practicality.
A leaner mixture would be already equivalent to one having CO2 filler. If there is insufficient fuel to burn all of oxygen in the mixture, it does not matter if it is O2 or CO2, it (non-fuel part/excess O2/air) won't burn. Also as jamesqf pointed out, gaming/fooling the ECU is done best through modding ECU sw /instrumentation.
I don't have an answer to the cooling brought by the dry ice, but somebody else more qualified should answer (and let me just meddle with interpretation of others' post
but what the heck, are not newbies allowed this to add to their post count?
)
Cheers,
hummingbird