check your drag bar and the ends. It sounds like one tire is drifting and wanting to go its own way. (Tie rod...) Its the smaller one on top, with one end on the pitman arm which comes down from your power steering pump. Chances are, one of the ends is getting loose at the knuckle.
Here is a pic of mine that I replaced w/my lift kit install. This also controls the position of your steering wheel and allignment.