My 2008 Ultra has developed that pinging noise that I've seen here before (like pebbles kicking up from the road). I use 93 octane gas and tried different major brands. I've added different octane boosters. I had the dealer check it out at my 10,000 mile service - said all was fine. Shell gas seems to help a little. It seems like a heat related thing cause it hardly does it when I ride when it's in the 50s. Gets real bad when I accelerate hard passing or going up a hill. It's driving me crazy. Anybody got any ideas who has had the same problem?