I had my hypercharger/jet kit installed by a dealer about 2 weeks ago. I have put about 200 miles on the bike since. My gas mileage has gone from 38.5 mpg to 28. After filling up on Sunday, when downshifting at a stop, I get a great deal of popping from the pipes. I also has the pair valve removed using the sherman coasters. Anyone have any ideas? I talked to the dealer this morning and he said that the gas mileage was expected and that he installed the jet kit just like the instructions told him too. He wasn’t very helpful needles to say. Anyway, if you have any ideas, I would appreciate it.