This has been a point of discussion for a short while now amongst the moderators. I have two points against it.

One, we don't really have the traffic, IMHO, to warrant subdividing the forum.

Two, I would really prefer not to divide into FI and NA sections unless the traffic became so overwhelming that division was neccessary. That, from my observations and experience, tends to divide the knowledge base of the forum. While FI inclined people may surf the NA forum, they're less likely to post.

In the future, when the site becomes more technical, as it has slowly for a while now, I would probably divide into a Tech forum and a Tuning forum... and/or an Engine Building forum as you suggested. That way, you get a couple of forums that everyone is using, rather than some forums that half the people use and others for the rest.