I have an 07 UC, and had a noise that was like little rocks hitting under the tank or fender.
If that is your noise it is pre-ignition. (pinging).
All you can do is add octane booster till it goes away (Short term)
Or add a fuel management system like a PCIII or SERT.
I have a PCIII and retarded my timing 2 degrees after 1750 rpm and my pinging is gone.

Mark

 

I have the same 2700 louder noise to 3000 RPM. It may even be there after 3k but with the Rineharts I can't hear it. I was not satisfied with my '07 until I had the IDS installed. Strange sounds (destrutive sounding sounds) and vibrations (destrutive feeling vibrations) have been converted to "regular" sounds and vibrations. There was a $100service credit a few months ago that applied to the IDS conversion among many other installations of parts.