Well, the filler neck is not leaking, there are no signs of leaks and I just made it leak yesterday, so that's ruled out. I'm still thinking it's the o-ring at the top of the tank. The gas pump will turn off after it leaks out a little bit under the car, so the leak is obviously near or at the top somewhere. My lines have never leaked either.
@BillBoost37, look at what I found when investigating the neck:
This is the evap canister isn't it? The big tube was not connected. Glad I went under there.
