I know that when you register a car in any of the metropolitan areas, you’ll have to pass the basic inspection: emission, brake, lighting (turn signals, brakes, high/low beam), horn, and windshield wipers. As far as I know, there's no fender requirements or noise restrictions... but I'll bet you'll get a "disturbing the peace” violation if you make too much noise early Sunday morning or in the middle of the night! Most of the local jurisdictions have control over noise issues.