Car stalls when stopped, and slowing down? Help!

Hello,
So I have a 2004 Lancer.  It was running perfectly fine, but long story short, it wasnt driven, at all for like 4 months.  I go to start it and obviously the battery is dead.  I buy a new battery, and it starts up just fine.  I decide to drive it to work, I get about 2 minutes away from the house and it kinda of starts to act like its going to die when I take my foot off the gas.  The gas light is on, so I pull into the gas stating, stop at a pump and it completely dies.  I put $5 worth of gas in it and start it and let it idle and it dies again.  I decide to try and drive it home, and it dies at stop lights, and start to act like its going to die, if I take my foot off the gas.  I would stop at a light, flip into nuetral and rev the gas a bit and it wouldnt die.  I decided to try it again the next day and the exact same issue.

What could be causing this?  The gas that sat in the tank for 4 months?  It ran perfectly fine before that.  Could it be something with the battery replacement?  I starts fine.. I know nothing about cars, help me!!