I do relate to INFP far more than I do relate to INFJ. I've been active on the socionics forum a lot more than here lately. When I first discovered socionics, I was certain that I was an EII-Ne. But then people who claimed to know the theory, started to type me IEI, and so I begun to wonder, study the types, and the differences, and I came to the conclusion, that IEI really is my type.
First of all, the four letter code of MBTI that fits me the most certainly is I-N-F and P, there's no denying that. Second of all the Fi of MBTI is different than the Fi of socionics. In MBTI introverted feeling is a lot about paying attention to your personal moods, feelings and emotions and making decisions based on them. They're sensitive, emotional, and since they might have issues with expressing their feelings directly, they might seek alternative ways of expressing their emotions via art, poetry, music etc. It important that the Fi stays true to itself, follows its passions and beliefs.
In socionics Fi all about a strong feeling of like/dislike towards something or someone, so the person has a clear set of personal values by which they approach others. These values are subjective and very strict making them appear somewhat rigid and judgmental. In socionics Fi is not about emotions, it's about values, the good or the bad, while one must strictly always follow the good. Personal distance is another strong feature of socionis Fi, so one values close relationships above everything else, likes to take care of the ones they love, and nurture the relationships that already exist with others. They are care takers, personal mentors, advisers, who always need to say and do just the right thing, according to their set of standards, everything else is a violation of their moral superiority among other people. They don't care about self expression and they are extremely stable when it comes to their moods and emotions, they can get stuck in one emotion for enormous matter of time, and hold on to it for its subjective value and to always stay consistent with whatever is perceived as good.
On the other hand Fe in socionics is moody, unstable, a little bit here, a little bit there, sort of floating all over its exterior. Beta quadra (IEI, EIE, SLE, LSI) is all about creating a personal image that would get yourself out there. Make you different and more important than others and that Fe functions as the primary tool for expressing this personal image. Fe in the beta quadra is about caring about the society's needs and making change, pushing, shaking the old, stubborn ethical standards of socionics Fi. Beta NFs need to express their personal values, beliefs to push society to their perceived vision of change (Ni) and they do so in the most theatrical yet artistic ways possible. it's important for betas to have some sort of a public voice, medium by which they can influence other people and share whatever is important to them. They want others to see who they are, what they believe in and why they believe in it. They want to influence people by emotional and ethical principles to follow their ideas of either ethical standards, a mood that should be shared among others or the vision they perceive as the correct one.
IEIs in socionics are perceiving types and unlike EIIs who are stable, private and more conservative, IEIs are moody, unpredictable and impulsive because of lack of their judging functions. Hence... yes I'm an IEI.