Today, I was able to sucessfully demo the problem for a tech at the local dealer.

In e-mode with air & radio off, it was barely audible to him in the passenger seat.

When he drove, he could feel it as well and said it was probably the "linkage".

He checked online but could find no factory bulleting on the problem.

He took it apart, re-packed and put it back together while I waited.

When that did not work, he suggested replacement parts.

I'll post any progress here.