You can check what funkycold mentioned and it may be the problem. Something else to check is the pin that goes through the springpack to be sure that it is not sheared. When it is sheared the axle will move front and back, effectively make the drag lonk longer and shorter, putting the steering wheel out of whack. I had a truck with a 4" lift once and the sway bar was hooked up but did not have any drop down brackets or sway bar disconects and when the spings would compress it pushed the axle housing back and sheared the pin, and it steered like how you desribed.
A good way to check the steering to see if anything is loose is to start the truck and have a friend turn the wheel back and forth and watch for things that move but shouldn't. If you don't have any friends to help when you want to check you can reach under the inner fender well and turn the steering shaft by hand back and forth, I don't have any friends so this is how I do it. /forums/images/graemlins/thumb.gif