All the EPA stuff, catalytic mufflers etc are to reduce smog ... HC and NOx. But the power reduction causes you to burn more fuel to get the job done thus increasing CO2. Its actually worse for global warming.
Same thing for cars. The first generation of smog controls killed power and MPG.
Maybe we'll see the same thing that happened to autos someday. Today's cars are more fuel efficient, more reliable, and safer than ever. And still plenty fast, without any modification.