Poor throttle response from idle is usually lean mixture in the transition between the idle system and the main system, or a deteriorated spark plug. If a new spark plug does not cure the problem, incorrect adjustment of the mixture screws is the most likely cause. Restricted flow (due to obstructed fuel filters or poor pump performance) is more likely to cause lack of full throttle performance than poor acceleration.
I suggest you replace the spark plug, and if still not happy, try richening both mixture screws one eighth of a turn (that is, turn anticlockwise). If that brightens it up, play around with the mixture screws a bit. Run it full throttle after warm up and lean the high speed mixture (H) slightly back toward where it was in the first place, listening to the exhaust. When you get it to where it sings the sweetest 2 stroke song, recheck the throttle response. You may or may not have to go slightly richer than the sweetest running, to get the right throttle response. Then, when it is really singing, lean off the idle mixture (L) slightly for highest idle speed, and recheck the throttle response once again. You will end up having to set one or both screws slightly richer than best performance, to get good throttle response.
