I may be wrong, but I believe I read somewhere that the O2 sensor and computer together (in closed loop mode) can only alter the fuel flow through the injectors by about 10% (change in pulsewidth). Later model computers have an adapt/learn capability (GM engines come to mind first) that possibly would be better capable of handling this increase.
Working with this as a basis:
Turbo injectors supply about 20% more fuel (for same pulsewidth), meaning that in closed loop mode you will always be rich.
In open loop mode you will probably be WAY rich.
Unless you are planning to go to an aftermarket ECU, you would probably be better off with an auxiliary injector tapped into the intake after the throttle body to handle the extra fuel needs of the nitrous.
If I am wrong about this, I would certainly like to know it - I hang out here to learn and help....

Brad