Car hunting what can I do to fix it.

[Gordz32]

Hey everyone. So I've got about 1800 miles on the chevelle since its been on the road. The one issue I have is that driving on the california highways the car is hunting pretty bad when it finds the grooves in the concrete. I understand that the tires come into play with this, but I'm wondering if I can change anything else to help with the problem. The car has a full airride suspension, Strongarms up front, and BMR adjustables in the rear. I also installed Howe Low friction ball-joints, AGR variable ratio box with stock steering linkages. When I had the alignment done I asked them to add in some caster and a little toe in but I don't have anyspecs as to how much they added. Sometimes its down right scary, driving in LA traffic at 75mph and the car finds a groove it likes. What can I do to help this? Do new corvettes have this problem, I know they run wide staggered tires. Also will lowering the pressure in the steering box help. It seems that when the car is off, the steering box has a little play in it( Like you move the wheel and it doesn't moves the tires).
As always, any help is appreciated.