Two people for sure, and maybe one person sitting in the way back of the car will make it drop enough for the SLS to lift the rear. Any deflection of the rear will cause the SLS to adjust. When the car is running go sit in the back with your feet on the ground, and you will be able to feel the rear rise up, assuming it's working. Like Kerry stated the system isn't hard to work on but parts are expensive.

-A bouncy ride in the rear is bad accumulators.
-Not lifting when weighed down it low fluid or bad pump.
-Sagging when sitting is a leak in the system.

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