I also think this has something to do with the torsion bars. Before the adjustment, my H3 also leaned to the left. The gas tank level did nothing for the issue. After I had the bars adjusted for height in the front, the garage (not a GM garage but one that specilizes in alignments) indicated that they felt the aligment was off from the factory. The garage spent an hour and half tuning, retuning, and fine tuning (only charged me for an hour) the alignment. It is now within a 1/2" of being perfectly level at all four corners and does not have a noticeable lean to the left like it did. And I believe the ride quality is a lot better, with less front end sway, especially in corners and curves.
Just an afterthought - could this problem be caused by the trucks being winched down to the cargo trains and tractor trailers for delivery to the dealerships?