I can't seem to figure it out...does anyone have any insights?
generally introverts are more difficult to pin point then extroverts because, duh, they don't express themselves with as much, so getting to know anything about them takes a bit longer, let alone indications of their type, particularly if you are an introvert yourself, since from my experience you guys seem to open up more easily with extroverts then with each other (though this anecdotal generalization might not always apply, alternatively it might only apply to sexual relationships and self-denying homo-erotic buddy-ism. also, introvert on introvert sex and extrovert on extrovert sex is a sin, i scribbled it in the corner of a bible i stole from a motel, so there you go).
but once you got close, INFPs and INFJs are not very difficult to differentiate.
INFJ: Ni>Ti>Fe>Se... naa, just kidding, that's just too awesome of a kind to exist in the MBTI. were where we? right:
INFJs: Ni>Fe>Ti>Se
INFPs: Fi>Ne>Si>Te
Ne vs. Ni:
if an INFx strike team tries to conquer idea-land in a creative or intellectual conversation, an INFPs creative spur would be the trooper going in with guns blazing in every direction they find, most likely ending up in a friendly fire mess that would turn the whole thing into a fiasco, while the INFJ's will be more like the precision sniper, most likely to kill the officer nobody likes while claiming it's the INFP's friendly fire which he'll get trialed for anyway but now gets the credits. why? because of...
Fe vs Fi:
take any sensitive social situation, find a time where what makes sense sociologically does not necessarily makes sense ethically, and the INFJ and INFP will declare war... actually the INFJ will declare it while the INFP will sort of slide into it opportunistically without really noticing, because of well.. P. the point is, if you hear the word "no this is wrong" and it refers to something that the person saying it wants to do but shouldn't do and then decides not to do, then its probably Fi, if you hear the words "no this is wrong" and it refers to someone else regarding something the person saying it has done a multitude of times themselves but has a reason to dislike the person they are referring too by saying it, it's probably Fe.
P vs. J
if you are getting to know them from... let's say a dating website or a blog rather then an actual conversation, there are some things that are a lot more likely to relate to Js -sticking to a special diet like being vegan or keeping kosher, being financially stable, obsessing about little details within their environment, etc.
and since you already expressed knowing the difference between Ti and Se... my job is done.