I have a Stihl BG-55 blower that lacks high end power...it's a little more than a year old and I blew out the air filter (which seemed fine), put in fresh gas and a new spark plug...all this helped a little but it still only has about half the power it should on full throttle. There does seem to be a lot of 'gunk' around the muffler and a slight 'ding' on the pickups (or whatever the technical name is) on the coil, and if a rock or something hit it. I know the fuel mix ratio is good so it's not too rich... Am I likely correct in thinking the reduced spark from coil damage would cause a low spark, leading to fouling in the cylander through to the exhaust?

Thanks!