If not working properly forget the deal. Any pressure differential below 4.0 psi in the appropriate level is a no go item. It is not. Something is really wrong and there are many components to check and replace very costly. If the differential pressure is near maximum 4.6 psi in climb and is decreasing by up to 0.5 psi in level flight with power reduced, the chances are good that the rubber landing gear seals are worn out.
Parts are affordable, work is high.