[instarx]

Hmmmm, the effect of CO2 in the intake is a more complex a problem than it seems at first glance. I don't think it is a given that it would cause the engine to burn leaner at all. The CO2 might make the engine run richer. The extra oxygen detected in the exhaust by the oxygen sensor might make the engine management system think there was insufficient fuel for complete combustion, causing it to richen the mixture.

Second, CO2 is a major greenhouse gas. So as well as using more fuel to drive the same distance you would be adding even more greenhouse gases to the environment from the dry ice.

Third, it takes a lot of energy (electricity) to make dry ice. That puts even more pollutants, including more greenhouse gases, into the air from the generating plant.

Adding CO2, in the form of dry ice OR compressed CO2 seems like a bad idea on several levels, in my opinion.