I have the Airlift 5000. I plumbed them separate to lift the rear and balance side to side. They keep your headlights out of everyone's eyes.
As already noted, they do not help with sway and will cause worse sway if you lift the truck off the overload springs.
I air mine then let them back down just enough to engage the overloads.
They do the job of raising and balancing the rear end well.
Last weekend I used them to raise the truck about 6 extra inches so I had a bit more room to work under it.