Thanks very much to all of you for your replies. What a great response!

Yes - I did check with the dealership to make sure the tech working on my car is a certified XF mechanic; I actually met him. (One of the many perks of multiple visits to have repairs).
In his defense, he is almost as frustrated as I am at this point. Currently the dealership is in "conference" with a senior engineer at Chrysler (second consult - first one failed obviously!), and the poor tech is caught in the middle. Oy! Oh - and he's the ONLY tech in town... the other Chrysler dealership brings their repairs to him. I think I'm stuck here...

Also - The service manager swears they have checked the main computer and chip in the car and that all is well with it. I don't know enough about it to push the issue, but maybe I should? I'm not very mechanically inclined, and feel like a complete moron when I'm talking with them sometimes.

And I did check into the Lemon Law... In Arizona (my home) the law only covers problems for 24 months or 24,000 miles whichever comes first, and I'm past the 24 months. So that's probably not going to work either... But I won't give up!

Again - thanks for all the great suggestions. I really appreciate it!