Welcome aboard, but I don't really think you have any hope of seeing 45mpg especially with an automatic transmission. I used to own a 2004 Toyota Corolla S (same engine, transmission, chassis - different exterior). Given that you have a Vibe (essentially a Corolla wagon) you are carrying slightly more weight than the sedan.
When I had my Corolla I noticed minimal MPG improvements with a cold air intake (Injen's worked best for me) and light weight rims.
In your case, I'd try over inflating the tires.
Hopefully you can utilize your scan gauge to prove me wrong.
