get ahold of RC ENGINEERING (russ collins)
told me once and i cant seem to find where i wrote it down
they sell a higher cc/min injector that is compatible with the busa ecu
they said it is "almost" a bolt on
they said the bore in the throttle bodies where the injector sits must be reamed a few thousands and new pigtails must be fitted to your wiring harness as their injector uses a different plug
they supply the matching plug/pigtails with the injectors
i think seb may have some higher flow injectors too
not sure if they are direct replacement or not