Where is First Byte TIme coming from?

[pmeenan]

It isn't related to the file size, it is about the back-end work that your server has to do to generate the page (database calls usually). Unfortunately we don't have any visibility into that from the outside other than how long the total time takes.

If you have a developer that can look at it, something like New Relic works really well for telling you where the server is spending it's time.