I assume there is a typo in your original note where you said you replaced the air bags and values, you meant VALVES. If so Hanno, who I know is correct, contact STAR MOTORS. Did you use rebuilt valves? If so there is a certain failure rate.
Now on the number. One for the rear. One for each front, and the the main valve under the hood. Total of four. Inexperienced mechanics mess this up all the time. They blame everything or everybody but themselves. With experience this is a great suspension system. It should last 6 years or more. I'm at 9 years now of trouble free use with a 1969 6.3. Follow Hanno's advice. Dan Smith, Oregon