Our cars have double wishbone suspension...which means:
A certain amount of body roll is necessary on our cars to facilitate proper camber, and an optimum (read that larger) contact patch (area) between the tire and the road. This results in more grip and better (read that faster) steering in and out of a turn.
I'm over simplifying it a bit, so this post isn't 10 pages long, but that's the gist of it.
So yes, while our stock S/Bars are not optimal for performance, and Supras definitely benefit from an upgrade, there comes a point where a sway bar with too much tortional stiffness will negatively affect handling.
I would say that if you are lifting your inside rear wheel in turns, you have exceeded that point.
Hope this helps. :icon_bigg