Weird this... maybe you should get a TL then
I've ridden behind you and you don't rev the engine more then the average.
Do what others have said before, check tyres, chain, ride smooth and plan ahead (and stop sliding the rear
)
If that doesn't help, do the plugs after that I'd look at the TB.
If it's any help, I was getting 120 miles (commuting through Aberdeen) and 160 on duals from a full tank on my curvy.