Is it possiable to remap a 2006 XK8's ECU yourself? I have seen software for other cars to remap the ECU via the OBD port.

 

No problem, there are many companies that provide the base software/hardware that tuners use.

For instance you could use http://www.cmdtec.it/index.asp, though only for the later denso chip, not sure if the 2006 is already covered, but this is just an example.
Very expensive though (which is why it would only make sense to use for tuners), and you still need to understand how to tune, ie also you need to know where to alter the data.

The cheapest way to alter the tune is to alter the maps which are included in the IDS/WDS software, but then again you need to know what fields to alter (I can assure it is not easy), and the uploading could be done via the IDS/WDS.

Another option is via the mandatory (from 2004) J2534 programming . Jaguar delivers the software for it (can be found on www.jaguartechinfo.com), but you still need to have an interface, where can be found here for example:
http://www.allworldautomotive.com/au..._ots19418.html

Would suggest to search the internet for this, I have no experience with this possibility.

Bottom line is that you already need to have a good base knowledge, and tehre are no cheap possibilites for the jaguar as far as I know.

Good luck!