What is this part called and where should it be/mounted?

http://i42.photobucket.com/albums/e303/declinepress/MarkVIII/60.jpg

http://i42.photobucket.com/albums/e303/declinepress/MarkVIII/50.jpg

that is the air ride shock control servo . it mounts on the top of the rear shocks to set the damping rate of the rear shock. if someone has replaced the stock shocks you can do away with it but plug the airline to it if it isn't already done. jd