I'm just not familiar with the new Stihl saws but would suppose a very small flat blade screw driver would do it; that and a digital tach was what it took back in the day when I worked on them. Btw, does yours have limiter caps on the screws? I was not aware until some time back that limiter caps were even being placed on them, I sure wish they were available way back when. I literally begged logging crew owners to take away all screw drivers from their operators lol. Here's a video that may help with the adjustments:
Good luck.