AL, sure you can chip them. I seem to recall that there are some chips out there that can be had at Mina Galleries (maybe only for the supercharged versions?). Even if there is no chip that you can buy, a good dyno shop should be able to tweak the programming a little more to gain you a fair number of horsepower. The factory tune is very limiting and is based around being as powerful as possible while also not making too much noise or whatnot. You take out that bit of conservatism and you cna free up some horsepower. But, before you do that, I would investigate if there are any modifications that can be done to the intake or the exhaust to ease any restrictions there. That way, when you use the shop, they will be able to maximize everything. I seem to recall though that the intake is definitely not a restriction and the exhaust offers very little resistance and not much can be gained. I am sure stepping up to a say a 50 or 40 series muffler will help some. Probably gain more by going with a properly built 45 degree crossover exhaust system. keep in mind that were you put the 45 degree crossover will affect if you are getting high end horsepower or more low end torque. it is all a function of the length of the tubing between the heads and the x-pipe. If you understand 1/4 wave tuning, then you can figure out the RPM that you are going to get the most gain.

 

Before you decide to spend the $$$ on a tune and pulley, drive the 470HP 5.0L SC XJ and see what you think. It has gobs of low-end torque, and may be all you need as a daily street driver. But if you're interested in 1/4 mile times ... well, you're never satisfied.

 

VelocityAP has a pulley and tune kit for something like a grand. The hypothesis is that these motors are capable of much more than they are tuned for, and that all 3 varieties are capable of 600 hp with a tune and pulley. I was leaning that way on my 12 XJ Supercharged, when my CPO was through, but am now apprehensive after the horror stories of reliability issues and huge repair costs. Others in this group have used this source with I believe good results. One comment I have heard is that Traction Control almost defeats a hot tune, unless you tune off. Then, when you turn it off, the car becomes a handful.

 

Before you get into tuning, please make sure you understand the downsides: https://www.jaguarforums.com/forum/f...tuning-206030/