If you are not within their scope of authority they have NO business setting standards for you. With my LE background I ran into problems with HOA's thinking it was the job of local authorities to enforce their rules as law! HOA rules are a civil contract between property owners within a development, period.
HOA rules are something you sign up for when buy within one of these development's, your choice if you want give up many of your property rights and be subjected to the whims of folks with nothing better to do than dictate
their personal views on others.
Good luck with your problem........My old G-38 with a Benett muffler would never pass your standards..........