Hi Harald, I too had a 2008 +4 4 seater, it had 2 sets of rear springs under warranty before I had a major row with the dealer and MMC and they (MMC) finally admitted they knew of a rear spring issue with supply and were changing suppliers. They came up with new rear springs of the 'latest set' (this would be well into late 2009)and it cured the problem totally. Others have claimed that the latest springs are made in India, I have spoken with the chap who makes them in Coventry as I have fitted 4 seat latest set springs to a 2 seater (also a 2008 +4) and the ride is superb and over a year its rear has dropped about 5mm as they have settled. The first question is are you on original 08 springs? If so maybe getting a pair of the current spec. 4 seater springs will solve all the problems. As to the Bilstein issue, I did exactly what you did and the car was almost dangerous as the Bilsteins provide a bump stop on the 4 seaters and of course you have removed it, I had the differential hitting the wooden heal board and it damaged the handbrake cable, that's the point the factory finally intervened and came up with the new springs.
