I'm having the same problem here. It feels like the vibration starts in front and pulsates to the rear, like a wave running through the car, every other second or so at highway speeds.

A little background... this is my third xf and I have experience this problem in both of my first and second xfs, and unfortunately now the third In both first and second xfs, it was tire related and I was running OEM recommended Conti's. The tire place rotated the tires (only left to right and vice versa) took care of the problem.

HOWEVER, I can't confirm if they dismounted the tires to make sure the tire manufacturer's recommended spin direction was complied with... so, I DO NOT RECOMMEND trying to do a left to right swap on your own. I'm merely hoping to help with the diagnose before tons of money/time is wasted.

On the xf that I have now, I'm not sure what I will do yet... the best option I can see is making sure the tire pressures are up to spec. If problem continues, I'll get a tire place do dismount and rotate left to right. By the way, on the current xf, I'm running Conti's on the fronts and Kumho's on the rear. Rears are brand new with 4k miles or so.

Good luck to us...
-Az4R1