Wow! Thanks for all the input. I did think the speedo had to be off. I ride at an indicated 90-95 mph on the 35 freeway miles, then I have about 10 miles of city. It just didn't seem that fast.
I have been using 91 octane, but after reading another thread I'll change to regular 87 octane. that'll save a few bucks, and should be fine. The bike is stock right now, and the previous owner said he had just had a service done. I'll see if i can't get some receipts from him.
So, if i change the sprocket, will I have to change the chain? edit: just read the 919.org write up. I think I'll do that.
I just ordered the SpeedoHealer, so maybe that will help. So does 35-37 mpg sound right with the way i'm riding? The bike has just under 10,000 miles on it, and is stock other than a K&N filter. (unverified, I guess I should check them) And I'll check out the plugs too. Anything else?