I'm not sure what's so hard about the line. Most municipalities already have the line well defined. They have noise limits that are different in residential

I'm not sure what's so hard about the line. Most municipalities already have the line well defined. They have noise limits that are different in residential and industrial areas, and are lower during normal sleep hours. If it means that you can't stomp on the accelerator in a residential area in your stock performance vehicle at night, so be it. Yes, some legally stock vehicles are loud when driven hard. So don't drive them hard when that's inappropriate.