07 10R, plugs changed about 2000miles ago. been running fine until this morning. Started bike, noticed it sounded like 'marbles' being spun around in tank. Bike started fine, but after idling a min or so i noticed it sounding erratic/stumbling. I let it warm up and go to take off and all she wanted to do was stumble and sputter until i got past 4-4500rpms. Higher rpms she runs fine, under 4000rpm or pulling away from a dead stop she acts like she wants to stall and runs pretty rough. At first I thought i got a tank of bad gas, but wouldnt it act up all thru the rpm range with bad gas? havent had the tank off since changing the plugs (done at a local shop) so im not thinking pinched lines. Any ideas on fuel pump? could the plugs take a shit in 2000 miles??