How come people say that the biggest injector I can run is 310 cc?
This assumes that you are not re-calibrating the ECU to the new injector size. If you don’t, the bigger injector will over-fuel. If this happens then the ECU will compensate to some degree using closed loop operation to reduce the injector duration. The limit of the long term closed loop adjustment is about 40%, which is close to the increase in size from stock to 310cc injectors.