Why not just do the injectors and pulley at the same time, and then re-tune properly for both?
In general, injectors need a tune. Otherwise, your ECU is trying to drive the new, bigger injectors using the duty cycle and dead times for the old, smaller injectors, which means too much gas potentially at the wrong time (i.e. - running rich and potentially missing).
Depending on how far off things are, the ECU might be able to adjust long term fuel trims while it's in closed loop and get close, but it won't be "right."