I bought a new Stihl BR340 at the beginning of this season from my local dealer. Over the last two weeks or so, I've noticed that the power just isn't there. I've got to run it at full throttle to get it to move just about anything. I went through the owner's manual and the first thing was to check the filter. When I pulled it off, there was gas/oil mix sitting in the bottom area, is that normal? Also, what else should I check to try to get the power back to normal?