I actually have the same problem with my F4. It starts at around ~5200 and ends at ~5700. I don't have any power loss or anything but I hate sitting there and hearing the sound. It's hard to describe, so I am not sure if it is the same thing you are getting. It's just a slight rattle or tinking sound, but pretty fast so it seems to be related to the engine.
If it is the CCT, is there any down side to it doing this? Like chain wear or anything?