Yes, thanx Maverick.
I will borrow the carlift in the next garage tomorrow and have a look. The reason that I suspected a vacuum leak close to the transmission was that the sound was coming from there,, I thought.
I know that its hard to determine exactly from where a sound like this originates from, so I just have to try and have an open mind. I can however announce that the x4 seems to work fine, but Im not sure that all of the lamps on the side of the lever works.
I also took a testdrive to see if the vibrations stopped. I found out that a cross on one shaft was moving in one direction. A previous grease monkey had missed that one of the bearing cups was not all the way in when he was mounting the cross in to its place. That made the cross movable at one direction, so I tighten it hoping that this was the reason for the vibrations, but no cigarr.
I was driving in around 85 kmh, and when I pressed the throttle it started again. Im not able to drive faster than 90 kmh as it is now. I suppose that Autobahn in Germany is out of the question at this time. Bummer......