What causes my car to sputter out and die?

I have a 2005 ford Taurus SE six cylinder. A year ago, due to financial troubles, I could not afford to keep the car's insurance, and I had it parked for a year. Now I am trying to get it running again and not having any luck. The car starts just fine, but after a minute or so of idling, or if I put the car in gear, it dies. While idling, the car sputters horribly, and I think it is backfiring. I have changed the spark plugs and wires, which were causing it to misfire before I parked it. Also replaced the dead battery. Today, we put ten gallons of fresh gas in it with ten oz of sea foam treatment. The car had less than 1/4 tank when we parked it, and the gas was too low for the siphon hose to reach, so we just added the new gas to it. Nothing has worked so far, and I need to move the car to my new home this week. Also, the fuel filter was changed a month before it was parked last year. Please help!