This site also sells just the Sportline springs and shocks, as well as the whole kit.
My car wasn't wandering a lot at 70mph, just didn't feel that tight, but didn't make any noises. The rear bushings were just about ready for replacing on the rear arms. New arms/bushings were about $30 each parts, and the car tightened up again.
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E