I have a 2008 GMC 2500HD 6.0.... Very stiff power steering at idle. If I take my foot off the brake it gets a little better but not much, and it gets worse as the truck warms up. TSB was no help, this is not normal, should not have to use both hands to turn steering. I've seen a pile of posts on this issue, but have not actually seen anyone come up with a fix for it.
I have flushed the system. No help.
I have replaced the power steering pump. No change.

Im up for any ideas, thanks!

Sounds like the bypass valve in the steering box is sticking or bad.