No I have not broke in mine yet but I know a dealer for Irvines that has said when they are broke in there is a noticable difference in the exhaust tone and you will be able to hear a big difference. The power will come way up after this as well.

As far as how many gallons, I don't think that is a good way to tell as all engines are different, but I'm sure 2 is close. My dealer said after 5 or 6 gallons you can really tell a difference.

If you just use some common sense with the irvine you'll be fine. Always make sure that you see a smoke trail while flying. If you don't it's too lean.