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This has been true for cars along. If you read the EPA rules they state you can’t change anything that alters the emissions output on a car. It also covers 1979 and later motorcycles. That’s why Triumph sells "For Off Road Use Only" mufflers for the Bonneville as an option. When ordering after market speed parts for cars, check to see if it meets EPA and or CARB standards. If they do, they have been certified. I’m sure one day, motorcycles will have to conform if they are required to go through emissions testing.