Who let the horses out?

[Gingernutz]

My poor old fzs600 foxeye has a problem. Someone snuck in overnight and left the barn door open so half the horses have focced off. She is fine up to 60 then slower than normal getting to 75 and then tops out at 80. Power delivery is smooth - no lurching or funny noises - but she feels  like a restricted bike. On the plus side I havent seen mpg figures like these for ages. 240 to a tank. The bike is a 2003 and done 60k miles.

So gurus whatcha reckon?  :\