Latest Update:
I so wanted to report that it was fixed today, but, alas, it's not. Measures I've taken since my last update are; replaced the crankshaft position sensor. Initially I thought this had fixed it because I could not get it to misfire in the garage. Out on the road with about 15 miles riding, I sensed a mild misfire, again still at the 4200 - 4250 RPM spot, but it was much less severe and more intermittent. Before that I tried disconnecting the O2 sensors, clearing the ECM with a battery disconnect and then running it that way. Of course this set a error code but the bike ran fine except it was still misfiring. I slapped the faring back on and rode her to work this morning and the very mild misfire was still there until I got 30 - 35 miles into my 46 mile commute where the misfire reared it's ugly, nasty, stinkin' head again and got really bad - like riding a bucking bronco anywhere around that sensitive RPM. It was cooler this morning so that may have delayed the issue. I also had a full tank of fuel and it seemed like the problem really appeared after a couple miles of lane splitting at low speed.
So changing the crank position sensor is the first attempted repair that seemed to make any difference in the bikes behavior at all. Ultimately it is obviously not the solution but maybe there's a clue there.
The only thing left to try is the fuel pump but I'm really confused why it would act up at a specific RPM, under light to no throttle, and affect the tachometer.