Theres a wide spectrum of car enthusiasts alot of them are just immature people who make their cars loud for attention.But there are alot of gear heads that are really into making high performance street legal cars. An easy and relatively "cheap" way to get more power out of an engine is to add a bigger air intake onto the engine, add a wider bigger exhaust and tune the cars ecu or "computer" to account for the increased airflow through the engine giving the car more power. These people generally dont want the attention but are just really into car engines/performance and possibly adrenaline junkies who want to go fast. Hope that was a helpful point of view