2 extra gallons
all you are doing is filling up the evap canister once you get beyond an extra .25 of a gallon after the click. This causes your fuel pump to vapour lock itself and WILL cause damage if you continue to do so.
Most fuel systems, once the evap canister is filled with fuel and there is any change in temperature to the plus side of when you filled (ie. weather getting warmer through the day) the fuel vapours created in the tank by the extra heat have nowhere to go and end up closing the check valve on the gas tank vent due to pressure. This in turn causes the fuel pump to try sucking fuel out of the tank with no relieve causing a vacuum in the tank that the pump cannot overcome and it shuts your car down to try and stop any further damage. If anything your car is running lean for 30-40 minutes before this happens and you run the risk of burning holes in your pistons, burning up valves and a number of other bad bad things.
Just because you can put another 2 gallons in doesn't mean you should.
