you are correct about the kick down but i belive that the intake manifold was a big factor as it only opens fully at 400 rpm before redline then as soon as it changes gear the rpm's drop to 4500rpm and the flaps close again i can feel a major difference in the way it pulls
http://i1217.photobucket.com/albums/...g?t=1299429139
thats with the valves open all the time ie. broken