Well RavensRoost and the rest of ya'll are on the right track. L screw ccw 1/4 turn certainly helped. Everything else looks pretty good (fuel, plug, filter). Still a little stumble, upon cutting the choke off for just a moment, but better. Ran it a couple hours and it did well as always once warmed up - but now I'm off and cutting once started instead. I now question if the screw is maybe the issue, as it seems to have moved slightly back to the original position. That would explain several Stihl techs claiming to have it fixed years ago only to have the issue reappear. I'll look into that further and report back. Thanks all!