Which upholstery shop did you use? I live in Washington D.C. and have a '95 SL320 with a semi-squeaky driver's seat (faint squeaks whenever I get in and out or turn in the seat) -- my dealer advised me that the only way to get rid of the squeaks is to replace the entire seat frame and seat cushion. According to the dealer, the SL seats are "spring-less" and cannot be serviced (somehow, I doubt that Mercedes would design a non-servicable seat). Whenever problems arise with the SL seats, the dealer says that the only remedy is to replace the entire seat frame plus cushion. Guess how much -- $2,200 (parts and labor).