Okay, so another thing worth mentioning:

I think I have trouble with long conversations. I'm great when it comes to short stuff, where I can be bright, bubbly etc and then get away. I'm also good in a situation with a reasonable number of people (3-8) because essentially it is a whole lot of little conversations, and I just add my own comments when I feel they are relevant, which is easy enough, and there are enough tangents in a group situation that I don't have to follow a conversation into any depth really. I think that because I find groups easy to be in (because I don't have to think up the conversation) I was mistaking that as being Extroversion???

But in a situation where I'm talking one on one with another person for any length of time, I find it hard to really connect, because I normally run out of stuff to say after about 15 minutes, and end up repeating generic responses. After a few hours of trying to think of stuff to talk about I can get really very mentally fatigued. This doesn't happen so much with a group though because there are lots of different tangents and everyone else is often coming up with new lines of thought taking the effort off me.

This can be the case even with my best friend. I don't remember how/why we became friends, I just remember we clicked at the time. But we both seem to run out of things to talk about after a while and I dislike the silences that seems to hang there sometimes. I feel like I should have something to say, and I don't.

Outwardly, we also tend to be rather reserved in our expression, not from any lack of friendship/trust etc, but things tend to be spoken about without a great deal of emotion or passion. Does that make sense? Or at least, nothing in our lives at the moment seems to really excites either of us overly.
It's not that we don't talk or share etc. Ultimately we do lots of that, but neither of us tends to place a particular judgment or personal bias etc on things, and I think that makes it hard for us to connect because things always seem neutral.

The most fun we have seems to be when we tease each other about something. Silly stuff normally. Like
Friends: "I remember I saw this car once..."
I interject: "Really, you saw a CAR?! Wowza..."
Friend: Glares angrily at me, or playfully calls me some sort of profanity.

Is that giving you any particular indications about my type?