I consulted an experienced rider about my fast idle problem. He asked if I ever checked the valve clearance, which I had not. When I did, the intake gaps were toward the upper limit (preferred .10-.20) but within spec. However I could not detect a gap for the exhaust valves (preferred .20-.30). I replaced the factory installed 320 exhaust shims with 300's. Now my bike runs as good as it ever has since I’ve owned it. It idles smooth with the idle speed screw backed out and I no longer have the high revving problem. I assume the engine was leaking compression through the partially open exhaust valves. I had to set the idle speed higher to compensate. From the current performance I don’t think the exhaust valves were damaged. Changing the valve shims was a fun straight forward project.
I was curious if you ever determined your problem with the fast idle condition? I had the same problem. Backing out the throttle stop screw resolved the problem on not returning to a slow idle speed, but then the engine didn't want to die well. I replaced the 22.5 pilot jet with a 25. It improved response off idle better than it's ever been, but still have the low speed idle problem. I'm guessing a plugged idle circuit. The more I back out the adjuster fuel screw, the better the engine idles. I'm afraid of losing the adjuster screw if I back it out further than the current 3.5 turns.