Can a catalytic converter change the amount of CO2 produced per gallon of gas?

One of the functions of the catalytic converter is the oxidation of CO into CO2 and another is to burn any hydrocarbons left over from combustion (which is also the primary function of the EGR system). So yes, the catalytic converter can change the amount of CO2 produced, but only by increasing it up to the stoichiometric ideal.

_

sure. It oxidizes hydrocarbons that are poisonous and CONVERTS them into water vapor and the thoroughly innocuous, ecologically inert and of direction happening byproduct of combustion, CO2.

A catalytic converter changes CO and unburned hydrocarbons to CO2. It also reduces nitrogen oxides to nitrogen. In short, a catalytic converter takes three pollutants- CO, hydrocarbons, and nitrogen oxides- and converts them to harmless gasses- CO2 and N2.

So to answer your question, a catalytic converter actually produces more CO2 by oxidizing more harmeful pollutants to CO2.

I think only temporarily. The main function of the converter is to have the CO2 come out of the tail pipe straight away, and not some time later as the result of smog eventually breaking down into CO2.

No, but it can ridiculously increase the amound of gas required to do a job.