One of the checks at the 600 mile mark is check and adjust neck bearings. It may very well be after the bearings set they need to be re-torqued. Pretty much normal stuff. Loose bearings can cause a lot of strange behavior not limited to high speed runs.
There is a thread around here somewhere that I ran numbers showing the power to weight ratio of the Diavel being better and no one wanted to see it clearly.
I rode the Diavel 1260 S with Termi exhaust a couple weeks ago... it is a beast and handles very well.