replacing carburetter with injector system

I am working on replacing a carburetter from a bike engine with an electronic petrol injector (similar to that used in car engines nowadays).

I have planned the whole system to be like this-



Although the system used in cars is more complex & uses more sensors, mainly to outperform carburetter, but my purpose here is just to make the engine run the way as it was with the carburetter.

The mass air flow sensor senses the amount of air flowing through the manifold during the intake stroke and sends this information to the ECU in the form of a 0-5V or PWM signal. The ECU then turns the injector on, and injector injects fuel in the intake manifold which mixes with the incoming air and goes to the engine cylinder through the intake port. The amount of fuel injected corresponds to the amount of air in the manifold to maintain the correct A/F ratio at a particular load.
One thing that I am finding difficult is that how would I know that what A/F mixture is required at a particular load for the engine on which I am working.

Please share your views on this.