The ECU will run the same duty cycle with the new injectors, and it will unsuccesfully try to compensate when it runs too rich. Basically, the ECU will open and close the injectors for the same amount of time as the old, small ones, but now you have a lot more flow capability, and that's where the richness comes from.. The ECU needs to be tuned for a lower duty cycle (time on/off) at lower RPM and part throttle, etc... If done right, you can get really nice streetability from some HUGE injectors with the proper tuning and adjustment...