On the Ford Duratec, the fuel pump will make the car spit and buck really bad coming out of a corner - especially if below half a tank.
The Duratec is also REALLY picky about spark plug wires, and will start trowing misfires like crazy at the drop of a hat. It happens under load - like you mentioned, going up a hill, and more if you step on the gas a little more.
I would strongly suspect spark plugs AND wires are the problem. Replace them all at once - bad plugs will cook a new set of wires, and bad wires will cook a new set of plugs. If you install them all at once, it should be good to go.