i would look for signs of Fi/Te, Ni/Se. i know that's the obvious route, but each really look completely different, because when it comes down to it, IXFP's and INXJ's are nothing alike functionally (behaviorally... any can resemble another, as in what "social-sub-faction" thier persona identifies with, but that's a whole 'nother ball game).
maybe an easier way to look at it is: Ji+(unaware to user)Je v.s. Pi+(unaware to the user) Pe. i say "unaware to the user" because most people aren't really aware of how their inferior affects them, but if you're uncomfortable with that, then think about it as being a C-grade-use when compared to their dominant A-grade-use. this doesn't mean that their inferior is worthless or even "bad", but pales in comparison to their dominant (again, what makes up the conscious part of the their evaluations or perception).
so, what comprises the "totality" (functionally that is) of the person? what is seen most often? is it a surplus of subjective value judgements central to the identity of the individual, mixed with an objective standard that furthers their dominant, or is it largely the work of hunches that are made up of many different componets that resonate subjectively within the person, hunches that are based off of "inner snapshots" of outer happenings and occurences (similar to the Si/Ne in many ways).