Jeff, thanks for the info.
Kazeyuki, like Fuzz said, I have been testing sway bars and will be posting up a bunch of data later. I will probably make a thread in this section and sticky it so the info doesn't get lost. I have not tested the ST bars yet, but I do have some lined up.
But as far as changing the handling, sway bars are very effective at adding roll rate without increasing the ride rate. Depending on what you're doing with the car, this isn't always the best thing. But for a street car, a sway bar upgrade with a slight spring upgrade is one of the better routes to take. For a track car, I would usually go with a much stiffer spring and a softer sway bar. But it really depends on the use and the rest of the setup.
Tim