Ok..........I was going to post in my old fuel thread, but I believe here will do more justice. Recently I rotated my gasoline storage (year old as always, with fuel stabilizer) . Encountered a problem I have never had , everything runs fine on the stored fuel, except my Stihl.
I disassembled , cleaned put back together ....same issue idle rough, no power or high rpm. Stalls when going to cut.....

Was the stored gas, everything............. cars, lawnmower, weedeater(4cycle) , generator, compressor, welder all runs fine......But the Stihl chainsaw and also a poulan chainsaw all had the same issues ........Fresh fuel cured the issues..........

Apparently the octane degrades enough in storage to affect the gasoline when mixed with oil it becomes useless.........

Thoughts............