Since I had the tank off the bike to do the valve clearance check I decided to put in one #4 washer to raise the needle. This seems to have improved throttle response especially when re-applying throttle after backing it off a little (if that makes any sense). I have stock air box, filter, jets and pipes but I do have an ignition advancer. It is a hot and humid day here in southern Ontario so maybe that is partly the cause as well.