If the idle just seemed to pick up with out changing any settings, keep an eye on it. That's how I found AS. I had several Oak logs on the ground to buck up to finish the job. I only took one of my Super 1050's. First log went fine, as I was walking over to the other log I noticed the idle seemed a little high, enough that it was spinning the chain. Made a few cuts and as I moved to the next one the idle was picking up more. From racing cars, I knew I was sucking air somewhere, I didn't know, at the time, that running a 2 stroke lean would kill it quick. Got the last cut finished. The next day the saw wouldn't start. Found AS and someone said to check the P/C. Sure enough, the rings were melted into the piston.
Learned an expensive lesson, don't run them lean and always have a back up.
Where was it sucking air at?