On all Pioneer 700 ( 2's or 4's), there are numerous reports of an internal muffler failure causing exhaust flow restriction. If you do a word search "muffler" on this forum you'll see pages of comments and experiences with this topic. It does appear there is / was a bad weld in manufacturing process that breaks with time and causes an internal baffle flange within the muffler to move around and hit the spark arrestor within muffler. Depending on where this loose flange ends up, it can cause a partial or a total restriction of exhaust flow. As more Pioneers are getting some miles on them, the issue is becoming more prevalent and reported. Hopefully, Honda will live up to its quality reputation and do the right (proactive recall) thing for all affected Pioneer owners.