Most times a plugged spark arrestor will give allow you to idle but will not allow you to throttle up.
When carburetor was rebuilt was the metering height set or did you just replace it with the one in the kit. The ones in the kit are not set correctly. If your metering is too low ie too lean then the carburetor will lean out.
A cool engine usually has surplus fuel mix in the crankcase which vaporizes as the engine heats up until it fully was up then the engine leans out.
Also Stihls seems to like to be ran a little on the rich. So when tuning tune idle mix first to best speed and increase slightly rich. After that tune the high side for spec max rpm leaning to the rich side if over speeding.
