The speedy cars racing down the street, without a care in the world. What is making a car go so fast? The engine has something to do with that because without HP (horse power). Without horse power your car will drive slowly on the streets. Many people mod their cars, to push the cars limits far beyond factory settings.
Some of these mods are not covered by the cars warranty. Fast cars are an underground culture with import cars being at most known. The culture of racing and modding your car to outperform other cars dates back for a long time. Thrill seekers are driving these cars to get an adrenaline rush.
Some of the mods include buying a new exhaust system for your car. It is said to produce between 10-20 hp. While that does not seem like much, but every little bit counts. Changing the headers on the car will make it perform faster, but they tend to be expensive.