I was out on a tree removal job yesterday, I used my 661 to buck and limb a large pee pine. The saw has about 3 gallons ran through it. The saw has a bog off idle when limbing, but its not like the 562 Husqvarna bog. the 661 bog is intermittent. other than that it runs great. Using stihl ultra at 45:1 with non ethanol 91 oct fuel. I tried switching the carb heater vent to winter but no change. Another thing I noticed was even when the saw was new after a long hard cut it has a lean lope when returned to idle then after a few seconds it clears up and idles normal. WEIRD. Would it be worth the time to reset the metering arm level?