I just purchased an 05 with 205K (not sure what that is in miles) on it - it has a 2.5" levelling kit and I'm running Goodyear duratrack 18" studded tires. (275/75/R18). I've noticed while driving at highway speeds that the steering feels a little loose and there's a bit of play - I find myself having to constantly adjust the wheel in order to keep'er straight.
I've heard sometimes the levelling kits can do this but I'm really new to trucks so can't back that up. Before I bring it in to have it looked at, I thought I'd post it on here and see what you guys think.