DynoDon
Moderator
The 2014 rule book has identified on page 23 that as of January 1st 2016, all Series B-91mufflers must be "strapped" or "safety wired" to the pipe. You will begins seeing the 4104 muffler designed by RLV that currently has the brace welded to the muffler. The brace is legal as per the 2014 rules. It is my understanding that all 4104 mufflers from here on will have this bracing. There will be a kit available for purchase for the older mufflers without the bracing welded to them. The bracing is a wire mesh type brace. As I learn more I will pass it on.