How can i tell if i have self-leveling suspension, i have a '97 740il w/o edc? also i have a good oportunity to get a set of rear bilsteins really cheap part #B46-2138 will this fit? also, when i buy shocks it has this plastic strip around the entire shock holding the solid metal bar of the shock into the actual tube of the shock. it's like if it were in the "absorbed" position but the shocks that someone wants to sell me doesn't have this strip holding the bar in, thus the bar is extended out fully, does this matter?