Hello folks, not sure if I have a problem or one time issue, after mowing two yards my Toro started acting like it was going to stall with I lowered to idle??? It has never ddone this. I had to increase the speed and left it running while I finished, I didn't want it to die and then have trouble starting it, got it home, switched out the fuel filter with a new one, old one was only a few months old and appeared in good shape. Started it up and ran it for about 30 minutes, high and low, no issues??? Did I have some dirt or am I looking at major issues?? Should I drain the rest of the gas? And start with fresh? Its the Kawi 13hp motor. Did a search and found a couple of clues. Thanks.