I've got a buddy who had the Eibach springs and airlift bags. And now I've got Hotchkis springs and airlift bags. Assuming you're springs aren't sagging (As in wearing out and lower than they should be) they're just lower than the stock springs. Correct?
What I've seen is that with 5psi in the bags, minimum recommended, the car sits about the same height, the bags just stiffen the ride a little. When you inflate the bags, they WILL raise the car AND significantly increase the stiffness of the spring / ride. Afterall, they are meant for towing. I can't tell you how much, exactly, they raise the car becasue mine is still in the garage awaiting summer. I recall my buddy's car raising up about an inch or so. When I had my 9C1 springs on with the bags, I would get about 1.5" of raise. Just working on the car in the garage and checking for leaks, it looks like with the Hotchkis I'm getting about 1" of raise.
BUT when I say the ride was stiffened I wasn't kidding. With the 9C1 springs and 25-35 psi in the airbags, its was a pretty choppy ride. And probably not something you want to have to ride on all the time.