Hi
I have been looking around for some exhausts for the XJ6N/Diversion. There is a company in France that supplies a wide range of manufactured systems.
Try this site http://fresco-exhaust.com/index.php.
I have already written to them asking what is envolved. It is the complete exhaust. Apparently there is some modification to the belly pan, but that is all.
I also spoke directly to Two Brothers in the US and they confirmed that they do make a system for the XJ6 known as the FZ6r in the US. http://www.twobros.com/cgi-bin/shopper?search=action&sku=005-25701&searchstart=0&template=Templates/TBRSearchResult-Simple-Yam-FZ6R-FULL-09.html
Here are some of the links on youtube.
Two Brothers ($1000)
Fresco Carbon (750 Euro)