For the last few months I've had a peculiar steering problem on my 2002 2500HD., and it is more noticeable when towing. When turning right at speeds over, say, 45 mph, the steering will wander, almost like it's in a turn, and then lets go a bit. It's easy to control, but it's just not right. I had my whole front end and steering box replaced last year so the parts are new. I've never heard of this before. Any thoughts or suggestions ?