I would start with the shocks, steering stabilizer, and front/rear suspension before I did any downforce body mods. Get the front and rear suspension checked out by a GOOD Tech before doing 80 again - at 105k miles you might have some soft rear bushings and/or distorted control arms. And as far as lowering, you might check the link under 'cars' at the top of the page for the Mercedes lowering and handling kit, called the 'Sportline'. Enjoy!
Increasing downforce on a w124...
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