I've found so much useful information in this forum but as all other forums it might be difficult to find exactly what you are looking for and sometimes you might even get the wrong answer.
Personally I found these links to be extremely helpful so I just wanted to share, even though I am sure most of you have already read these already.

Jaguar XJ6; Jaguar X300; 1995 Jaguar XJ6 3.2 Sport

Jag-lovers' Ebooks Book Index

Jaguar Vanden Plas "The cats meow": List of X300 Technical Service Bulletins

Go LPG - Common used X300 faults

Please feel free to add more links if you have any more of similar type