2001 S600 vibration

My car has been in shop several times. Replaced motor mounts and it didn't help. They say everything else checks out.

Car wobbles while in Park....idiling, in drive at stop car sometimes wobbles. Also, at 1900 rpm just driving easy there's a whirring noise above the normal engine noise.

Both these things started happening after they replaced steering rack at 18k. They also had to replace upper/lower control arms to get rid of creaking sound while turning wheel. Now car vibrates in driver seat and empty passenger seat headreast vibrates tremendously at 78 to 81 mph....which is exactly my speed range for highway driving. Wheels and tires have been indexed and also on car balanced perfectly (throughout entire speed range) to 140mph.

I've done some on-line research:

They (dealer) says laptop system says MAS Mass Airflow Sensor reads ok......I've heard this can be the culprit for idle vibration. Could the MAS read ok and it still be defective?? Also, could it be the ABC system reacting to taut?

On another message board a gentleman in Belguim says hydraulic hose form steering system can send vibrations in park or idle at stop.

While driving, I've heard there has been a problem with parking brake system causing vibrations.

Anyone have input on these two problems. Thanks in advance.

PS Great car....but boy, have Mercedes become "buggy"!