I aksed my dealer to do it too, but the guy I talked to said "No". I asked why, and he said that it would not be w/in factory specs if they did. So, I asked him what the factory specs were on the torsion bars on the AV, and he didnt know. Turns out, he didnt even know that you could adjust the torsion bars and didnt know anything about the AV.
My 2 cents: There is a sticker, from the factory, next to the torsion bars that says somethign about getting a re-alignment after adjusting them. They are also easily adjusted and require no special tools. Had Chevy meant for these not to be adjusted, then they would hvae required a special tool to adjust them and they would also have not made it as easy to access/change. I could be wrong, but its just my pennies worth....