The stock injectors are 4 hole. The 12 hole injectors give a better, finer spray mist than the 4 hole do. Better atomization should lead to better power and gas mileage.
YotaMD did dyno testing between freshly cleaned 4 hole injectors and 12 hole injectors to validate these claims, and the results were underwhelming:
https://www.youtube.com/watch?v=D1zq1Dl_IhM
That said, going from dirty 4s to clean 12's might make a positive difference







