You'd be better off throwing the old airbags away. Even though they may look ok, As they wear, they become porous. When that happens, the compressor runs more than it should and burns out. I went though this with our 4.8is it was an expensive night mare.
I think I had a newer version of DIS. There is a diagnostic routine that tests the whole air suspension system. During the test, you measure the height of the vehicle to make sure all sides are equal. It was during that portion of the test where I lowered the vehicle using false values...
I still have DIS but we sold the X5 years ago so I can't tell you exactly how to do it...

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2005 4.8is Le Mans Blue
2011 35D Space Gray