I’ve had this appear twice on my 2011 2.2 facelift XF. First time was a faulty injector which showed up immediately when connected to the diagnostic unit. Second time the fault was intermittent and nothing showed up on the diagnostics. As a trial and error process seemed inevitable, my mechanic suggested I start with the fuel filter which is a cheap option. I wasn’t so sure as it had already been replaced 6 months prior to this but decided to give it ago. Lo and behold no more restricted performance. Been fine ever since and that was approximately 8 months ago. Not saying this May be your issue but it’s a cheap option and certainly won’t do any harm to try..?