[88carrera]

From the description of your car's sagging problem, it is difficult to believe that the shock is the problem. It sounds as though there is something else amiss with the rear suspension system. The shocks on a Porsche that has not been tracked would be expected to last longer than the mileage yours has accumulated. Plus, it is not the shocks themselves that determine the height of the corners, rather other components of the suspension system (spring perch height, spring lengths, etc.). I would take this car to a shop with a good reputation for working on these cars and have them take a look before opening my wallet to have the shocks changed out.

Have you ridden in a 996 C2 with the M030 suspension? If you have not, I would highly recommend that you do so before you make this change on a daily driver that you do not intend to track. You may find it too harsh for your liking.

My '03 has the M030 option along with a set of H&R springs that lowers it about 1.25 inches from stock. It handles beautifully, BUT for a daily driver you might find it too low (careful about scrapping the front spoiler on just about everything, including dead squirrels) and the ride too stiff.

Just my $0.02 worth.