Is modifying a car illegal?
This depends on where you live or where your car is registered. Basic bolt ons should be legal in many areas as long as it passes vehicle emissions/safety inspections. Again, this depands on what you modify or change in your car. Please check with SEMA at http://www.enjoythedrive.com for more information. For more detailed info, the FTC has setup a page with concise information in full guts and glory.