What a roller coaster. A friend of mine has a 2006 4.8is in Imola Red. mmm
He's been having the same issues with the light and his is squatting on the drivers side most of the time. He's considering the $1500 swap that ditches the whole system for traditional suspension.
Honestly, I don't know how to advise on this because it seems like it could be a bottomless pit. My X5 has 185k miles on it and the rear bags are still working as they should, I guess the simpler the better in this case.
I sent him a link to your post to help him decide. Lots of great info. I hope you remain error code free.
