I have not noticed and issue with having power, just that it over heats if I pull power to go up hill. I keep up with the others I ride with who all have 700s as well. It did overheat after a long drive at higher speeds when we got on a road that accessed the park. As soon as we left the level road and started to climb the temp went up.If it was the muffler issue you would have a noticeable loss of power under load or at high speed. Is that something you've noticed?