If it's the classic ethanol-rotted-a-pinhole-somewhere-in-a-fuel-system-component (which makes it impossible to tune correctly), you might want to price out just replacing the whole carb and the small seals and the fuel line itself, all at once. If you go with the replace-just-this-one-little-gasket at a time, you won't know when the next ethanol pinhole will rot it's way through to daylight (and a now random amount of air in the combustion chamber) in some other part of the fuel system. The fun little, not always possible to spot pinholes can change as the saw warms up, or is started on a cold morning, etc., etc., too, I believe.
But first attempt to put a good new tune on your saw and see if it can hold that condition through several hours of operation. And maybe that is all you need.
I am not a saw mechanic, I just learn things the hard way.
