OK, met with the "master tech" at my Chrysler service dept today, he seemed to know about the update and was willing to do it, since I was having other warranty work done at the same time (Radio/CD, broken foglight housing, transmission leak). Mentioned that the car shifted like an E-Class, and he just smiled! Will advise on what they do, and if it makes a difference...

He also said that the supercharger addition would only require minor transmission mods, mostly programming. Could this be true? He seems to know his stuff, and has a healthy distain for the XF without bad-mouthing it! (which I read as honesty).