DEATH_AWAITS_YOU

When the malfunction occurs, can you adjust the volume from the steering wheel's volume control? If so, the problem is in the radio. If not, the problem is in the amplifier.

What DTC code did you get, exactly? There is no "lean" code for an oxygen sensor. If you did, however, get a lean code, it indicates that the engine is running out of fuel. How does the engine operate under wide open throttle? Your problem is most likely that the injector driver's are failing in the engine ECU. The reason you may not be getting as many MIL's as you think you should, is because the ECU doesn't think anything is wrong. Replacing the ECU should take care of your problem. I would advise against buying a cheap aftermarket 'rebuilt' unit as they are not very reliable. Good Luck.

The problem with your rear suspension is most likely either or both rear height control sensors. If you don't have access to a scan tool, you can try this-Does the height control work at all? IE Can you raise the vehicle with the height control switch? If so, the concern is most likely the sensor(s). If not, you may have a leak in the rear air bags. Look under the vehicle and see if the rubber stoppers are sitting on the rear diff. tube. Also, listen for the pump to be running near the rear wheel. If the pump is running but the vehicle won't raise, you probably have a leak in the rear air bags. I would advise against using aftermarket springs/shocks as this will greatly detract from the value of your vehicle. Good luck.