Right, small update. I've looked under the car and as far as i can tell everything seemed fine exept for the rubber bushing support that the driveshaft goes through under the middle of the car. It seemed dry and made a "dry rubber, cracking" sound when moving it. You could move it a cm or 2 back and fourth, but the driveshaft wasn't really loose. Could this be related to the issue? To me it seems a bit too small of a problem to cause the vibrations, but i don't know....