Sluggish acceleration above 5000 RPM

[Ray]

Foot peg vibration can precede failure of the front end of the cardan. I'd avoid riding until I took a look. It's now a warranty item..., so....

The vibration appears to be engine rpm, not road speed (rear wheel RPM) dependent.

(Or a harmonic.... Not sure you can pick up the sensation of a 4 kilohertz vibration through your feet. The changes in acceleration suggest the problem lives downstream from the engine.)