I first thought that an INTJ was just an INTP (or rather an ENTP) without Ti. In order for an INTJ to apply logic to his theories as an NT would be to develop something that would test existent systems of logic, Ni. It originates ideas for the Te system to judge, so that the INTJ can learn the ways of Te and perfect his plans. (That is one way of looking at it. You get my point.)
I'm not sure how true the former is. I obviously have pretty decent Ti myself. I trust outer systems and my inner system quite equally. I still have a driving need to use Ni all the time. I think Ni is actually my way of collaborating with Ne when Ne needs a helping hand (although often a hassle to me.) I have a hard time getting Ti to judge Ni however. Other than that I'm straight Ni and Ni to Te.
I always see INFJs with barely any Fe where Fi is used more. I'm like, wouldn't that just make you a retarded INTJ?