[Jach]

Found some references again.. INFP and INFJ would mostly differ in Conscientiousness (the J being more so). Extraversion-Introversion correlates with Big 5 Extraversion (on the E pole), Thinking-Feeling with Agreeableness (F pole), Sensing-iNtuition with Openness to Experience (N pole), Judging-Perceiving with Conscientiousness (J pole). (http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.555...)

If you're on a boundary you might get more insight from breaking the Big 5 into the 10 aspects (https://www.ncbi.nlm.nih.gov/pubmed/17983306), e.g. Conscientiousness can be split into Orderliness and Industriousness. You also might benefit from having someone close you think models you well (if available, this is the loneliness thread...) answer the test questions for you to see what they get, or perhaps as effective you answer for yourself and also for someone else you think you have a good model of to help highlight differences in degree.

Lastly since MBTI tests are still sketchy, go for a Big 5 test, read about the Big 5 (my first link has some useful descriptors), and forget about MB. For free, http://www.personal.psu.edu/%7Ej5j/IPIP/ exists and is the longest one I've seen. I've read that https://work.coach/assessment is useful. The only paid one I've heard about recently is the rather steep https://www.understandmyself.com/personality-assessment but I suspect like IQ tests paid might give the most utility... (I'm not part of the JBP fanclub but do listen in on him sometimes, so again grain of salt...)