My car has recently clicked over 100000km since new and is due for a service. I was thinking of changing the spark plugs but I see from the Vehicle Maintenance Sheet Jaguar X-Type 2.0, 2.5 & 3.0 litre that I'm a getting a little ahead of things. No doubt this would have no adverse effect on the engine etc but if I can get a bit more out of them then why change the plugs sooner than neccessary. I know that I will need to replace the upper and lower manifold seals when getting to the plugs, I already have the plugs and seals. If I'm going to the effort of doing these should I be looking at replacing other parts while I'm at it, to save having to replace the manifold seals again and again? I see that the Lower IMT Valve o-ring can be hard to get to without removing the manifold (apparently), what else would I be well advised to replace at the same time? As always the info here is extensive and thorough, thanks in advance.