I also think I am ambiverted. Some people have thought of me as ENTPs before...weird. I don't tend to look up online definitions of Ni or Si, instead, I observe it in real life with real life ISTJs and INTJs. The INTJs I've met seem to act more introverted than they really are. I could be wrong, but it's just an observation. A discrepancy I've noticed is ISTJs usually have very good memories and are detail-orientated, that is surely not the case for me. I'll read up more on Socionics when I have the time.Well, I see Te in you but you're introverted and less connected with the external world than ENTJ's. So that leaves INTJ and ISTJ. I don't know if you're Ni or Si, but I 'd suggest you to not to stick to online definitions for coming to conclusions about Se and Si. Socionics descriptions offer more realistic descriptions of sensors, not limiting Se users to short-sighted retards and Si users to docile workers, policers etc.
Idk about INTJ for me. Could be, but most people say that I'm Ne>Ni and I don't think that I'm introverted. I'm ambivalerted/mildly extroverted, and most INTJ's are quite introverted.
Ni is a hard function to spot in others, from what I've seen. It seems like a dormant function that only appears sometimes, then again, I could be wrong.