My Stihl 390 is in need of a little tune up. It had two problems, one is that it would stall when cold and the other is that when I am cutting full bore on a log sometimes it will bog down and I have to ease off then go again. I fixed the stall by just turning the idle up a little. I am wondering on the other problem if I should just open it up a quarter turn for more fuel or what do you guys recommend?