Any connection between the valve and bag can be a potential source for an air leak. Both over and under tightening lines up after you work on any air suspension can also cause it to leak. If you suspect a leak, try soaping down the fitting on the front strut.

You may also need to reinitialize the air suspension system (Ill let someone who has the factory system chime in on that because I dont know the procedure)..

And lastly, it sounds like this guy clearly doesn't know much about the X's systems to which I will simply say it's time to find someone who does.

__________________