two things i can think of, have you checked the castor angle on the front end they make wedge spacers than you can use to adjust it, also if you have big tires on the front on wide rims it can make it follow the cracks or seams in the pavement. The 4 X 4 guys add a horizontal shock=.stabilizer to help out. you might want to check out front and rear sway bars. they have to match your springs or you could get over steer or under steer if theyare not set up right