This struck me as interesting. I was at Bruce Rossmyers Harley Davidson this Biketoberfest, and caught this interesting bit of info that the parts counter person was telling a customer. I guess the customer was concerned about the heat from the engine. Not sure what year his bike was, but the parts person asked. "Is your bike stock?" Customer said "yes." Well the parts person said that if you was to change out the stock mufflers and put on some other pipes like the SE pipes or Rush pipes other than stock the engine would run cooler. So when I heard that I got really interested. Is this a Fact or is this just a sales pitch. When a more free flowing muffler is installed, can it make the engine run cooler? He was saying that "all that back pressure in the mufflers just caused the engine to run hotter."