car wont idle evenly right rear sinks down overnight

You could have a hole in that air bag. Here is the test; turn the truck on and let it idle. You should hear the air compressor filling the air reservoir on the driver side. Once it stops you should go around to the side that is going down at night and place a bullet or torpedo level on the bumper and watch it. if the bubble moves before the air compressor turns on again, you have a hole in the air bag.