I had sort of the same problem... high revving engine and random 'dying' mid-ride. I finally realized that my gas cap was preventing the tank from venting properly. I drilled a tiny hole in the cap and that solved the problem completely. Try running the bike with the cap unscrewed. If you do drill a hole in the cap, make SURE you cover it at least with a rag when you're storing the bike so the fuel doesn't get condensation, etc in it.
Also, I'm assuming you are checking the air/fuel mixture screw to make sure it's not vibrating into a different position during your ride... that can cause the high revving too... good luck!