[MT-2500]

What year?
Has it done it since it was new from day one?
On the floating is it a side to side float or bounce up and down or just pulling left to right?
What does it do on sharp curves?
First things I would check is front end alignment and sway bars and shocks.
Also tires and tire pressure.
Does it still hold good ride height?
Has tire sises or ride height been changed?

Find a good GM dealer and ask sales and service and parts departments to check what the different parts are on OFF road and regular suspension.
Shocks and springs and tires would be the first things that may be different.

I would also contact the 800 customer service no in your owners manual and explain the problem.