ISTP: Ti - Se - Ni - Fe
INTP: Ti - Ne - Si - Fe
Both of these types are associated with Ti, or process oriented, Einstein-like thinking. With Ti in the dominant position, they are excellent at troubleshooting, breaking apart, and analyzing problems. The ISTP combines that with auxiliary Se, gravitating him towards hands-on, concrete challenges, such as mechanics, sports, and construction. The INTP combines it with auxiliary Ne, leading him to synthesize theories and conceptually examine abstractions. The ISTP is better at noticing what is present. The INTP is better at noticing what is missing.
However, the test aren't all that accurate in determining one's mbti type. Also, nobody will posses 100% of any type's traits. A more efficient way of identifying your main type is to thoroughly study the eight cognitive functions.
In a nutshell...
Perceiving (Irrational) functions:
Se = physical sensation
Si = database/map of sensual experience
Ne = possibilities, ideas, concepts
Ni = symbols, connections, associations
Judging (Rational) Functions:
Te = military-style, court-like thinking; results oriented
Ti = Einstein-like, process-oriented thinking; blueprint-like
Fe = social harmony
Fi = personal morals and values
dominant > excellent, early childhood (a person naturally uses his dominant function with excellent skill in comparison to his other functions, it is extensively developed in early childhood)
auxiliary > fairly good, adolescence
tertiary > mediocre, early adulthood
inferior > primitive (just barely enough to survive), midlife
Extraverted (e) functions are objective and connected to the outside world. Introverted (i) functions are subjective and locked within the constructs of one's mind. So extraverts perceive the world more objectively and introverts perceive the world more subjectively. Extraverts are more externally involved with the world, while introverts are more reflective and introspective. Extraversion is concerned with breath, while introversion is concerned with depth. Types with a dominant judging function, including IxTP, are more concerned with making sense of the information they have gathered than they are with gathering new information. The opposite is true for those with a dominant perceiving function.
ISTP:
https://answers.yahoo.com/question/index?qid=20140927183017AAu1dET
INTP:
https://answers.yahoo.com/question/index?qid=20141011060135AAOnHXH