Hi Roy,
I bought my 2011 XF-S just over a year ago; had two problems...
Awful grip due to cheap Chinese tyres
Vibration from the front wheels when braking
First was a no-brainer - 4x Pirelli P-Zeros, sorted!
Second was a bit more challenging to my pocket, namely new discs and pads for the front, but now completely fixed.
Sounds like you have a different problem though, as mine only vibrated when braking.
Could you, maybe, have a damaged wheel? Or just a duff tyre?
I wish you the best of luck, and hope to hear of a resolution.
Cheers,
Jon