Hi I'm new also and also have the 2.2 xf, mines the 193ps 2012 poverty spec one :D. I found a decent company up the line (I live in devon so anywhere is up the line to me) who promise 55bhp gains from a map aswell as a dpf and egr mod (cough cough). if you where interested I could pass you on, they are very well known and have a good reputation.
also have you looked into twin exit exhaust's like the v6's? I think its got to be done, the single exit really lets them down!