Is modifying the exhaust appearance illegal?

[LeSavannah]

If only the exhaust style is modified, it is not illegal; however, modifying the exhaust sound is considered illegal. Precautions for modifying exhaust pipe styles: There are many styles of exhaust pipes, and not any one can be used. Before modifying the exhaust pipe, pay attention to the original exhaust pipe style, whether it is straight or curved. Many car owners choose straight pipes for smoother exhaust flow, but arbitrary changes may not be suitable for the exhaust system. Choosing the sound based on car displacement: Many car owners put a lot of effort into modifying the exhaust pipe to achieve better exhaust effects. It is not uncommon for car owners to only modify the tail section of the exhaust pipe, but this approach is actually incorrect. For the exhaust system, the part responsible for noise reduction is not only in the tail section but also concentrated in the mid and tail sections of the exhaust pipe. When modifying the exhaust pipe, avoid modifying only one part and consider more aspects.