1997 Cadillac Deville Suspension Problem?

[Jason]

I have a 1997 Cadillac Deville. If you have ever owned a cadillac deville, or if you havent, you may know that the rear suspension is adaptive. This means that when there is weight in the car, the rear will use special adaptive suspension to level out the car and make it to the appropriete suspended height. There is a problem with it. It will raise up and level out, but over the period of about30 minutes of driving, the suspension will have slowly lowered (like it has slowly lost its raised height). The rear of the car will be about eight inches from the ground when it has a moderate load in the trunk. I think it may have a pin sized hole in the vaccuum lines to the shocks, or a pin sized hole in the air ride suspension bladder. I need an opinion about this problem from someone who knows what i am talking about, and how much it may cost to get fixed. Thanks, Jason Webb