Loss of Gas Mileage

Last year I was getting 120-130 miles before my gas light was coming on in my 2007 GSXR600.  This year it is coming on between 83-100 miles.  I haven't made any performance mods to the bike over the winter.  Why the loss in Mileage???????  

i have an 07 GSXR750 and i am still getting 130-150 mileage out of mine a year later and thats with a power commander and after market air filter. its all in how you run it to be honest. when i run about 5 over the speed limit i get good fuel use but if you run it like you stole it forget about it. anything over 80 on a constant basis will make it chug your gas big time. if you try that and you still get bad gas mileage then have the bike looked at. even the slightest problem could lead to that. Good luck  

I haven't changed my riding style from last year to this year. I have a power commander/pipe last year.  The last two fill-ups I got 102-105 miles.  Its confusing me,and my mechanic. Thanks for your post though