I have a '14 XF and was wondering what the difference is with the "S" version. I see it has the same 3.0 V6 with supercharger, but what gives the extra 40 hp? Is it a tune or does it contain different parts?

Also, does anyone have experience with xcentric exhausts?

 

On a '14 XF "S" means the higher tune 3.0 V6 twin turbo diesel with a few other extras such as bigger front brakes, which was never imported to North America.
For the 2016 XF, the new shape X251, "S" means either the very similar 3.0 diesel (again, not available in North America) or the higher spec 380 hp 3.0 supercharged petrol, which is the same engine fitted to the F-Type S. I think but I'm not sure the lower spec 340 hp petrol (same motor as yours) is in the 25T version.

 

That's some good insight, thanks for the heads up! I guess they really ARE different.. I just saw 3.0 supercharged and realized one had 340 and the other had 380, figured it was just a different tune or upgraded parts off the same base.