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Yes you are on the right track.
There has been a service bulletin for that type of concern. Here is what it states.
File In Section: 03 - Suspension
Bulletin No.: 02-03-99-001
Date: June, 2002
Some customers may comment that the rear of the vehicle sits low and will not return to normal operating height. The customer may be able to hear the ECAS compressor running.
The compressor check valve may be sticking in the compressor housing, not allowing the ECAS compressor to build pressure and raise the rear of the vehicle.
Follow the service procedure below to correct this condition.
Tighten the cylinder head screws (1) to 5 N.m (44 lb in).
Tighten the air supply line fittings to 2.25 N.m (18.5 lb in).
Tighten the air spring compressor to frame mounting bolts to 25 N.m (18 lb ft).