the factory injectors are tiny @333cc these need to be changed, for the Y33 version engine,mabey Y34 also but i havnt seen one, the injectors are the same style as sr20det and rb25det injectors so plenty of upgrades are available.
Max boost is a different question, really depends on tuning along with many other variables, Why are you interested in max boost? rather than setting the engine up for a certain application?