Problem With rc 750 injectors please advise

[turbo20hatch]

Ok I have an s-300 i got my car running fine with the stock injectors (240)
Today I installed rc saturated 750 cc injectors changed the fuel trim to 750cc
left stock size at 240
apon starting the car it ran lean af like 1.30 lambda of the meter
adjusted the overall fuel trim to 75% now car started to run good lamda 1.0-1.6 but when give gas leans out again
Why do i need to use 75% over all fuel trim and also could the be some other issue causing this?
I am using a walbro 255 fuel pump with an aem adjustable reg at 43.5 psi also have high flow fuel rail and new pumbling through out.

[Spunkster]

You will have to completely retune the fuel maps when you change the injector size. The tab for injectors size is to help you get closer to the proper fuel trim, but you will need to make further adjustments to the overall fuel trim before making changes to the tables themselves.