I'm still changing types, I'm fair sure that I used to be introverted, I was the shyest thing you'd ever see in my childhood, I didn't like talking to strangers, my parents friends, or anything like that, I would occasionally ride my bike to my other friends house, but it's only one good friend. That means, that I was probably introverted, and slowly built up extroverted qualities, I test as an ambivert, I would definitely consider myself an ambivert, the tests line up with that consideration, some things I prefer to do in an extroverted fashion, others an introverted fashion.
One thing I really wonder about is the Ts capacity to be nice. I find that I am actually quite a fair bit more generous than I though, and there's no logical basis for most of it, it's just self sacrifice (although that's quite an exaggeration). I've also noticed that introverts can act rather extroverted when they are in the company of one or two close friends, even in a large crowd of people, they can often be the loudest, most talkative ones there, and in my case, I can talk to complete strangers as much as any extrovert provided I have something to comment on. I don't feel drained from talking to people, it's quite the opposite, they give me quite a lot to think about, and I often get sort of... drunk? after talking to people. One thing that I have noticed as a sign of introversion, is that I actually get headaches after being extroverty for an extended period of time, I'm pretty sure that's a physical sign of a secondary function in play.
Lastly, I need to work out if I'm more INTP or INFP, and from the looks of things, I'd have to say, INTP is pretty well ruled out. The way Ti builds a sort of library or data is somewhat alien to me. But then again, I don't think I can actually see the effects of my Fi, I suspect that it's just hard to tell without knowing full well what you're looking for.