Well i'm not sure how much power your setup would put out, but i would be running something like 440 or 450cc injectors, and no stock Honda has injectors this large (as far as i know).

However it seems GTR injectors (which are 444cc) are suitable, as well as possibly injectors from GSR Lancers (though i havent verified that myself).

New injectors you should be able to find for maybe $150 each.

The reason i dislike adding an extra injector is that there is no guarantee that all the cylinders will be getting the same amount of fuel in that case.

I think a unichip should be able to control this, another cheapish option is a TSI unit which is about $1400 installed and tuned.