Efficiency and power are not equivalent. All you need to do is look at the most powerful (hp per liter) cars and the exhaust systems they use for proof.
The people were talking about are slapping shitty cat deleted straight pipe exhausts on what are typically engineered to be economy or family cars, or small displacement motorcycle engines. People who don't see the offensively selfish stupidity in tripling or quadrupling the noise output of their mode of transportation just to get an extra 10% power, if that.
They're not running million dollar F1 cars around closed environments dedicated to the purpose.
They're not running million dollar F1 cars around closed environments dedicated to the purpose.