im not here to convince you to run one. im here to state facts.
cat converters reduce harmful emissions by converting them to less harmful gasses. NOx leads to smog, acid rain, and contributes to global warming (blah, blah, blah). CO is, of coarse, an oderless, colorless gas that is extremely toxic to humans. partially burnt hydrocarbons also add to smog and have been known to cause cancer if the concentration is high enough. converters are very effective at reducing all 3 of these pollutants.
a properly functioning (not clogged) cat converter will have zero effect on mileage or power one way or the other.
i realize i sound like a greenie weenie defending converters like this. in reality, environmentalists annoy the hell out of me, as do any extremist groups. but due to the fact that catyletic converters do not have any negitive side effects, and i dont have to go out of my way to utilize one, means i see no reason NOT to use one....and i especially wouldnt go out of my way to disable one. the fact that its highly illegal to remove a converter is just icing on the cake. you can do whatever you want. but suggesting other people follow suite without properly informing them first is selfish, rude, and ignorant.