When I washed my bike today I thought on your problem some more.
Although you said 3200rpm, ANY GEAR, I'd still check your rear wheel for missing balancing weights. Sounds wrong 'cos the balancing weights are speed related, NOT "RPM in any gear" related, but as I'm at a loss - check anyway. You'll see left over double sided tape perhaps if any were there that aren't now.
Otherwise.... I'm all out of suggestions
