Shaking steering wheel

Hi, I need a bit of technical help with my car. It's a 1996 w461.337 and I
have a heavy shaking steering wheel between 80 and 90kmh. There is also a
tendency for it to start with roughness in the road (continues for a few
seconds until the steering dampener reigns it in). I've done the following:
New bilstein shocks, new link rods, new steering bar, new 18"alloy wheels,
new tires in the right size, wheel alignment and balancing done, tightened
steering box, replaced front axle ball bearings, replaced steering dampener.
With all this, the steering shake of the whole front end persists and I don't
know what else to do. Thanks.