Old tired 4.0 reborn?

[Grumpy47E]

New to the forum as a member altough have visited frequently. I have a '97 Disco with the 4.0. I am planning an engine rebuild this summer. I have been looking into making the lower half into a 4.6. (Oh by the way did I mention automatic tranny.) What I am trying to find out is about the ECU issues I might have by changing injectors to improve the fuel flow etc... Bosch injectors most likely. Will I have to reprogram the ECU? If so how, where? Wil the increased performance require the reprogram?
Thanks. Look forward to the responses.