Don't know if it's the same sensation you're getting, but the front end in my 03 Screw feels a tad "floaty" sometimes. I've checked, triple checked, and had a buddy of mine go through the front end numerous times both on a 2-post lift and on a 4-post lift (with the weight on the suspension) and I have yet to find anything wrong with the truck at all. It seems to be "just one of those things" that you have to look past.
I'd have the front end checked out completly and then go from there. If nothing is found, ask the tire dealer to swap the tires for something else to see if the feeling goes away. Most good dealers nowadays have some sort of ride guarantee that helps in these situations.