I bought a 2000 model xj8 engine for my xk, on comparison the injection system has been updated, my question is what is the vent ,breather pipes in the middle of the injection for and where does it go behind the throttle body, Or should I reinstall my 97 injection system??

 

The 2000 AJ27 engine is not a direct replacement for the 1997 AJ26.

It can be made to work but requires significant swapping of parts. Here is a link to get you started on what needs to be done. There are others that a search will produce.

AJ-V8 Engine compatibility question - Jaguar Forums - Jaguar Enthusiasts Forum

Good luck!

 

After many hours of swapping parts and general fiddling i have now managed to get the car running and driving (replaced gearbox at the same time.)
So now i have a load of AJ27 parts up for grabs if the trade for some wheels doesn't pay off!!