On my XF the boot lid can be made to open by itself, there are 2 Springs one on each side and they are behind the side walls off the boot.
The Spring comes from the curved arm and are attached to a Bracket towards the rear lights, and i've used a strong cord to adjust the Springs, you can pull the end off the Spring out of it's present position and hook it into another position nearer to the rear lights.
I've tried the boot lid adjusted with 2 Springs but i found it lifted the boot lid too quickly, so i've reverted to just using one Spring.
And it opens with the key fob and the switch below the steering wheel, but be careful when driving because it you hit the switch the boot lid could fly open
Regards Tom.