Why wont it start?

[Oscar029]

Hello. I have a 4AGE engine, in my GTs with only 80000 original miles. Now, When I first got the car, I drove it home, but, now that it sat, It doesn't want to run. Let me explain. You see, I try and start it, and it will start!!!!, but it will not stay on! It will start, then shut off in about three seconds. I was wondering what it possibly could be? I bought a new starter, fuel filter and pump, new sparkplugs, and alternator for the car. It just will not stay on! I even Bought a new Mas airflow sencor to make sure I had a good fuel and air mixture going into the motor. Ehat else could it be? I was thinking maybe it could be the injectors. What do you guys think? I would really appriciate the help. Thankyou.