I installed an AirLift 1000 air spring helper kit on the rear of my 1999 Buick LeSabre. I didn't spring for the inflater, aside from my trusty floor-mount bike pump. Usually it's me in the car, and occasionally 3 other people. The 3 others would make the rear of the car sag, despite new struts all around. What pressure do other folks run their kits at to have the benefit of the assist in the back for an unexpected load while keeping ride quality?