To your question, he can simply continue to make noise complaints to the local PD (doesn't require a friend in the department) until someone looks into it. Eventually someone will. If you are cited, CA can make it expensive for you. As I understand CA law, it is unfriendly towards modded vehicles. I would suggest that your vehicles could be written for several violations if you don't have CARB numbers or certificates for every modification.
If he really wanted to be evil he could also report you to the California Air Resources Board for violations to the smoking vehicle laws and then you could then have the environmental wackadoodles after you. For that one there is a website for making the complaint.
Time to play nice. Pissed off old guys know how to turn up the heat when the other party is in the wrong. Go by his house, apologize for the noise and try and be the good neighbor.
If he really wanted to be evil he could also report you to the California Air Resources Board for violations to the smoking vehicle laws and then you could then have the environmental wackadoodles after you. For that one there is a website for making the complaint.
Time to play nice. Pissed off old guys know how to turn up the heat when the other party is in the wrong. Go by his house, apologize for the noise and try and be the good neighbor.