Very self-protective xNFP here. I swing between E and I on the test and get 51%-55% either way most times. I identify with both ENFP and INFP descriptions. Certain situations seem to propel me towards one or the other.
Falling in love seems to be one of the things that makes me more introverted because I don't want to get hurt. I'm in that situation now, and the person I feel that way about is an INTP. We are close friends and we've been sleeping together lately, so it's not like I have a crush on some stranger who I don't know or understand all that well.
However, my first awareness of the depth of my own feelings came from me interpreting some of his words and actions as meaning that he has feelings for me. It looked for all the world like Ne was asserting itself, and I have actually been acting very extroverted lately, so that would be the first thing that pops up, as I understand the functions.
Fi seemed to quickly follow, with much overthinking about how I really feel about him, and a very reluctant conclusion that I'm falling in love with him. (The reluctance has to do with some of his convictions, which I think would end up hurting me but are more manageable in a friendship).
So now I'm wondering if my first inkling, which seemed like Ne, was just wishful thinking and projection because of flip-flopping to introversion due to a fear of getting hurt.
I don't know if any of you can answer this question directly, but I'm hoping maybe you can help me recognize the differences between Fi and Ne. This latest scenario is just one example of a dynamic that has happened before and caused me a lot of stress every time.