Motorcycle Repair: noise while trottling up, full trottle, harley shop

Question
2007 Electric Glide Ultra Classic, odometer 1400 miles, no modifications.  Returning from a trip, 80 miles into the trip, stop for fuel, left station back on highway in 5th gear without down shifting went to pass truck gave full trottle at 55 mph with radio on heard a scratching and slight pinging sound. Once I passed truck went to a maintain speed of 65 mph, at that point trottle up again  
in 5th gear noice returned. Tried again at different speed and different gears only when trottle up full trottle do I hear this noise.  Harley shop took it for a ride said they only heard normal sounds.  Have you heard of anything similiar to this on 2007 and 2006 bikes I did not hear this for first 1400 miles.

Answer
Haven't heard anything on these other than you must use at least 91 octane or you will get pinging under load at low rpm in higher gears. Remember, they recommend 2000 miles for break-in which means no steady riding at any speed, should vary speed and gears.