Ha, you guys fall for that propaganda on the interweb!
Catalytic converters reduce more harmful stuff than they might increase NOx. And cows are creating a heck of a lot more ozone problems then catalytic converters are. And running a modern engine on unleaded fuel without catalytic converters creates even more bad emissions than the older cars that ran on leaded. So when you remove your cat(s) you are polluting even more than we did back in the 60's & 70's! But if you don't like catalytic converters, then go out and develop a better emission's control solution that doesn't rob power or efficiency. But I doubt you'll find a better solution that reduces smog emissions without having another adverse effect.