I have a 91 560sel with 242k miles (and it doesn't have a flaw) however, when I fill the trunk up with luggage and put my two teenage daughters in the back seat the rear end sets down far enough that the tail pipe scrapes the chassis over bumps and railroads. My mechanic says my nitrogen air bage system needs to be replaced. He said an alternative would be to switch to a 450's suspension so I could put air shocks on. I would prefer to keep the car original. Suggestions? Comments. Thanks.