Nope, although preferably xj12 out of respect for the xjs.
Usually by persons who prefer fresh air over the significantly reduced value consequence of owners handbook, service manual and spare parts manual no longer being reliable and who are either prepared/able to do it themselves or are very wealthy. Lots and lots of examples, stories and support on this forum.
Imo only worth it if you adopt the very latest aftermarket engine management tech, is what I am doing. Also simplifies everything. Otherwise, if legacy tech is used, no worthwhile improvement, more expensive and a lot of parts NLA, complicated and more difficult to maintain than Stromberg’s, imo.
Considerations include: fuel pump, fuel filter, fuel cooler, intake manifolds, balance pipe, crank case ventilation, throttle bodies, air filter boxes, valley cover, throttle capstan, throttle linkage, fuel rail and injectors, brake vacuum hose, air injection system, extra and supplementary air valve or IACV, overrun control valve, water rail, thermostat housings, HE heads and pistons, exhaust manifolds and cowlings, ECU, injector power supply, ignition control system, spark distribution, all of the wiring and more.
https://1drv.ms/b/s!AiSPBKa26IcchMxtWzeqA4wVVhifTg
Happy to expand on any of the above if you are interested.