I'm am sure there must a thread on replacement calipers on a 2009 XF----not the stock but 2 piston. I have searched high and low on the net and can't find any.
Any help would be much appreciated.

 

It depends on which calipers you are talking about, OEM or after market.
If OEM the only two pot calipers are the 380 mm fronts, all the rest (355 and 326 mm front and 376 and 326 mm rear) are single pot.
The good news is the 380 mm two pot front calipers will bolt straight up to a car that came with 355 mm fronts, not so sure about the 326 mm fronts but maybe. Also I understand that the NAS (US and Canada) market never got the 326 mm fronts anyway.
If you can source some 380 mm fronts it is a simple plug and play swap, no instruction guide needed. But of course you will need the caliper brackets and rotors as well, and at least 20" wheels to fit over them.