changing injectors

[Superscan811]

The amount the injectors flow is worked out by the Duty-Cycle.
The ECU has a Duty-Cycle based fuel map.

SO

If you change your injectors from 450cc to 750cc, you would need to reduce your Duty-Cycle by 60%.

I take it both your old and new injectors are LOW impedance.

If not, there is a lot more work to be done because a 450cc LOW impedance injector will flow differently to a 450cc HIGH impedance injector, if given the same duty cycle.
The reason, HIGH impedance injectors take more time to switch on and off.

Cheers.

[amgis_obrut]

you need about 5.5cc of fuel per hp

to work out injector sizing its
hp divided by number of cylinders x 5.5

eg
300 / 4 x 5.5 = 412cc per cyl