I wonder if the E93 is contributing more?
Have you tried top up and down and compared the volume?
80%+ of us all are all E90/E92
There should be no vibration at all, ever, esp in the steering
Did your installer skip some isolators on the install maybe or something?
Don't think it is the welds, the tips are still held there rock solid I bet.
Maybe climb underneath and give it a really good inspection and make sure everything is done right.