[f5fstop]

Have a reliable shop do a test to see how many amps (milliamps) are being drawn when the ignition is off, and after a wait of 20 minutes. Modules go into sleep mode after approx. 20 minutes, so the parasitic drain will go down. If there is a high drain, then start pulling fuses until the drain drops. This will tell you the circuit that is at fault.
It might be the air suspension system again.

The Onstar module draws an extremely low parasitic drain.