989,791
People aren't supposed to modify the exhausts etc., on motorcycles, but many do. When the bike reaches 3 years old, it won't pass its MOT test with many of the aftermarket exhaust kits. The usual dodge is to temporarily re-fit the original exhaust, just for the test, and then revert to the noisy one afterwards.
I don't like noisy exhausts; they just draw attention to the bike - the police can hear it coming from miles away - I prefer the 'stealth' approach.
Also, many of these noisy systems actually
reduce the performance of the bike - this seems crazy to me. If I had to put up with more noise, I'd want better performance in return.