hey buddy.
i had the same problem as you.
the cables must stretch out or something over time. the kickdiwn cable id the one right nest to the throttle cable, on the top of the pedal lever. i wound up putting two zipties on my throttle cable, so it was tight all the way up, and the butterfly opening all the way up. i had no kickdown when i did that.
when i looked at it again, i started messing with the kickdown cable. i noticed that there is a point where it activates, and it is probably within 1/4 inch of its full extension. i discovered this by pulling on it. with the zipties on my throttle, the pedal was stopping before it got to the point on the kickdown where it opened up. so, what i did was tighten my throttle, but disable my kickdown.
so, in order to fix it, i put one ziptie around the kickdown cable in the same fashion as the ones around the throttle cable. it works perfect now.
i'll bet all you have to do is the same thing.
let me know if this works out for you.