[niles]

Your symptom is consistant with an out of balanced footprint.
Imagine a four legged table; If the front left and right rear suspension was "longer", ie had more weight on them. The "long" diagonal carries more then 50% of the weight. Accordingly the right front/ left rear carries less. This makes the car handle very assymetrically.
Solution: find someone with a set of scales and get a even weight footprint on all four corners. Don't think you can do it with ride height, that sometime compounds the problem. My recent example I measured, plubbobed, etc and thought it was perfect. Set it on a set of portable race scales corners were off over 200 lbs.
The first setup is set the corners and then realeign. Then experiment with pressures, etc before messing with springs. Springs will not cause that unless you have a "flat/weak" springs which exaserbates the footprint problem.

gn