Well I have been around nissan and people who modify them for a very long time. It seems nissan always runs injectors that can handle a bit more then the stock HP output. So I am betting injectors will not even need to be swapped for 7 psi or so. I do know of a kit for the HR16DE where they did not swap out the injectors at 5psi.
As far as tuning I swear that I read about that our ECU's can be flashed. I don't think we actually need a piggyback or anything for a mild turbo setup. I believe the company is UpRev that is able to do it.
Seems all you guys really need is an exhaust manifold and then your good to go.