Yeah i pretty much tried everything you have before i replaced the compressor.

2 New Arnott bags
2 Front level sensors
New Relay

And then replaced the compressor,unfortunately for me i also had to replace the suspension control module,i've got around $3K in the suspension so far,touch wood its going fine now.

The arnott compressors are a much better deal than the stealers,i don't know how they can justify the price when an aftermarket supplier can sell them for nearly half price.