2008 1200c, V&H slip ons and stage one breather, HD supertuner. I am hearing a strange sound on hard acceleration in any gear. Sounds light metalic almost like belt squeal on a car but not that loud. I do not think it is engine ping. Seems to happen when it is hot, above 180 more near 200. I only run 93 and been using mostly BP. I tried changing brands last week to Chevron with no results. I checked shields on the pipes and all seem to be fine, all clamps tight.