My friend and I have a butterfly valve catbacks setup on our cars, but keep in mind that our set up has the valves are located way in the back where a typical briefcase muffler would sit.
Most of these butterfly valves can traced back to bulk wholesale items found on Alibaba and from our experience they do
NOT like heat. The electronic motor that opens and shuts the butterfly valve may fail eventually. Personally that hasn't happened to me yet but there are rumors. Lastly, the valves will seize and get stuck either full open or full closed. My friend is dealing with that right now. Fortunately, we have warranty so our local muffler shop replaces them frequently (about once a year) no questions asked.