Steering problem

I have 1988 Blazer K5 the truck has been lifted 9". 5" suspension and a 4" body lift. It runs on 35x12"50. It has a 350 with 81,604 miles. The truck wanders to the left or to the right when I am driving down the street or when it hits a bump in the road. My question is can I adjust the power steering box to fix this problem.