That's not true, there are cars that can break noise regulations stock, even mass production models: https://www.thedrive.com/news/stock-hyundai-elantra-n-fails

That's not true, there are cars that can break noise regulations stock, even mass production models: https://www.thedrive.com/news/stock-hyundai-elantra-n-fails-noise-test-leaves-owner-stuck-without-registration https://www.thedrive.com/news/stock-hyundai-elantra-n-fails-... The key difference is even loud factory exhaust setups leave room for relatively quiet operation depending on how you drive. That Elantra driver was an idiot: he went in a town and drove in sport mode and drove in a way that forces extra loud pops If he hadn't been forcing it the car was perfectly capable of not making excessive noise. — The $100 bozo special on the other hand has none of that: it's always loud and obnoxious. In fact it gets more obnoxious at cruising RPM because of drone. There are aftermarket exhausts that try to match the factory-style "not loud by default", but they're expensive because it takes careful engineering and integrating things like valves and Helmholtz resonators.