stihl "wood boss" chainsaw bogging down

recently purchased a used stihl chainsaw. it has worked great until now. the only work i have done to it recently was to tighten the chain. however, i don't feel that i over tightened it because i can still pull up on the chain and have enough slack to see most of the bottom teeth on the under side of my chain. while i was using it the other day it got to the point where i was cutting a wedge shape out of a log (i wasn't even that far into the log) when it started to bog down every time i pushed the gas. it also is doing this thing now where i put it into the stop position to kill the engine and it don't stop immediately like it use to. i have not got the time yet to back off on my chain a little bit just to see if that has anything to do with it.

thanks any info would be greatly appreciated!