hey guys, abit of a question. being a car novice give me a chance learning pretty quick

my setup includes:
jdm 1jz - unknown internal work/cams
hks cam gears
top mount gt35r - 3inch dump/turbo back
decent size FMIC
running standard 380cc yellow injectors at 60psi base fuel pressure! though a regulator ( bad i know. but the car come like it and runs virtually fine apart from being a pig on fuel and occasionally stalling as i come to a set of lights)
i have dyno sheet with 223kw atw @ 21psi in QLD weather/98 ron fuel, im sure theres a shit load more in it with a decent tune

anyway, i want to look into a set of 550-650cc injectors and lower the base fuel pressure
1. so its better on fuel ( off boost ),
and 2. so im not maxing the injectors out and causing any problems

ECU is a greddy emanage blue,

How should i go about it?. i know the emanage has a fuel trim option with standard and upgraded injector inputs ( but its thrown out since the fuel pressure isnt stock)

or should i drop the injectors off with the car and tell the tuner i want this this and this?


much much appreciated!