As the others, I'll tell you 300 miles is not correct.

Right now, I'm testing my MPG and I'm at 1/4 tank with just over 110 miles on it. I want to see my MPG difference before and after my next tuneup this weekend.

You mentioned you have not changed the air filter.. CHANGE IT! that WILL give you better mileage, not dramatic.. but it will. That's a fact.
You'll be surprised how much difference oils can make too. Right now, I think one of the best on the market is Amsoil and Motul...

if you do have real bog, not clutching related, it could be caused by dirty air filter as well, but on a fuel injected engine it would have to be pretty dirty to make a difference.

 

Uhm...in all actuality...changing an air filter that desperately needs changing will show a SIGNIFICANT improvement in fuel economy and performance.

The oil difference between leading brands is up for debate. Don't pinch pennies on oil and go with a reputable brand. Once you're with a leading brand for motorcycle oil, you simply can't go wrong.