I agree that shocks are not the issue unless they are seriously binding internally but then you would have a very rough ride. The air bags aren't the issue either, they only lift the truck and if it takes 90psi to get the truck back to where it should be with factory suspension and no load then the factory suspension has failed or has been altered.
It comes down to broken springs, hangers etc. Or, the truck was lowered intentionally and the air bags were added to keep it from bottoming out under load. You might want to find a similar truck and compare the suspensions.