Your neighbor could be right and so could be your local dealer. There could also be some glitch in the EFI as they not all set codes. If it does it to such an extent it should be relatively easy to find.
Real unlikely to have reversion with SE slip ons unless they were modified in some way, because they are almost as restrictive as the stock mufflers.
Real unlikely to have reversion with SE slip ons unless they were modified in some way, because they are almost as restrictive as the stock mufflers.