Im Having Trouble With My 1999 Sts Rear Suspension, I Dontknow If It Hasair Suspension, But I Never Have Heard The Compressor Come On If It Does. When Its Just Occupied In The Front It Looks Fine, But Ifi Had A Couple Of People In The Back Seat, It Just Dropsand Neverdoes Comeup Umtila While After They Have Gotten Out, And It Feels Less Powerful With The Rear End Down. Any Ideas?