Yes of course, there's a number of threads on swapping engines, but before you do that get a set of compressions to check if there are compromised cylinder liners. If it takes a long time to crank before ignition, that's a sign and also oil in the induction tube/TB, generally the top end of the engine is too oily on a failed Nik unit. Another thing to check is the timing chain tensioners/guides as early units have plastic parts that fail. Pulling a cam cover will confirm which you have fitted, hopefully they'll have been updated to medal. Along with this, the plastic T stat housing is another item to update to metal.

An OBD reader is a great way of locating and fixing things so that's a priority, many are using the ELM 327 OBD reader, all you're after is the codes & fuel trims.

I'm not sure but are the 2 cars different models in AJ26/27 engines? Or do they have the same engine?

 

I feel kind of funny answering a question here, since I'm in the company of people who know volumes more than my few days of research have taught me, but it is my understanding that some time after my '99 was made, Jag started putting iron liners in the blocks. They call those the AJ28 engines. I will do a compression check. My car starts right away, no delay. I guess the restricted performance mode could be caused by the transmission problem (A-drum). I was also warned by a veteran X308 owner that vacuum lines on the throttle body are frequent gremlins. Thanks for the heads up on the code reader, I'll check that one out. My main worry is in getting something that doesn't support Jaguar.

 

Sorry I missed this question- its NOT the cam design- its the vvt changing the phasing that gives a HUGE low speed torque benefit and often a power benefit also.

Specifically its the intake valve closing point, mainly, or IVC, at low speeds you want to close it early, at higher speeds you want to close it later. Its true that the cam profiles NEED to be optimized for the use of VVT- typically the optimal duration comes down about 10-20 degs.