Hey markc, mine is the same way. No matter what gear I'm in, as the tack approaches 3K, the vibration starts. It's in the engine I'm almost certain, and the vibration travels all through the bike. I've learned to live with it. 14 hours from Nashville to St. Joe I lived with it if the bike ran 68/72 mph or better (that's about when 3K is hit). 12 hours to Sturgis as well. Sometimes seeing anything other than a blob in the mirrors at highway speed is not possible. At least I can tell when someone is getting close (which mostly I see others getting farther away).
I have not had the bike to a dealer for anything other than it did see the 500 mile service before I picked it up on Des Moines, Iowa. I noticed it right away & it's still part of this bikes charactor.
Anyway, I wanted to let you know that there are others out there with the same "RPM" related vibration.
See ya.