Welcome, Bob!I know in my 2006 base, I have been able to fill up just beyond 12 gallons without forcing more, when the pump stops. The tank + fuel line/system = around 13 total, I believe. As far as city mileage, I really do not know. I just enjoy getting through a work week full of city driving and not having to fill up until the following Monday. Highway? A typical drive to see the in-laws of 155 highway miles, I am able to do that using only about 4.5 or 5 gallons. So, in the neighborhood of 33 or 34 MPG. And that's usually with 100 pounds of dog and luggage. Also, the clicking sound is not something my Vibe has experienced, but here is a helpful thread others assembled to explain the fix, appropriate parts, etc.
http://forums.genvibe.com/zerothread?id=29575Best of all, it should cost you under $50, if you are able to this on your own.Good luck, and the SEARCH link in the top right is your friend. Not the Google one, just below that.
Steelies to the rescue.