First off don’t do anything to muffler till you make sure the carb is a fully adjustable one. If it doesn’t have a wt-194 with both high and low jets you can’t adjust to more open muffler.
Second make sure you know how to tune a carb properly before doing anything to it, only reason I say this is I don’t know your skill level and you just asked about how much and what side of key to remove to advance the timing. Lastly you can’t run this saw without a base gasket so don’t even attempt a gasket delete because the piston will slap the band on the edge if not removed. Far as timing gos I remove about 20 thousandths off the key and you install it so the flywheel gos further counter clockwise looking at it.