here's what I found. The #3 plug was horribly fouled, which explains the rough running I had in the last 50 miles or so (but it really wasn't all that bad). All the other plugs were OK, so I'm ruling out a weak coil as that would have affected 2 cylinders, not just one. I was also smelling raw fuel after shutting the bike off recently, which I know was the vacuum shutoff. After cleaning off the plug fouling the engine runs normally again, so I'm less suspect of single cylinder issues like bad plug, plug wire, or loss of compression. I don't think any of those things would have gone away just by cleaning the plug. So the vacuum shutoff valve is in the trash, I did a 10 mile test ride and filled the tank, now to put a few more miles on and see if the mileage returns to normal again.