My mustang dies right after I start it up?

Ok so my car starts up just fine but instantly dies.. Iv tested the EGR valve and the solenoid. My codes are saying the MAF is faulty but before I go spend $120 on one is this my problem??? Please help me what could it be. I was thinking TPS or timing is off but I just need to know like I said it has no trouble firing up but unless I'm giving it gas it'll just die. I tried to drive it and when I shift the RPMs fall quick and let's say Im in 4th going about 45-50mph and I just let off the gas pedal it'll jerk forward. Also it's backfiring bad when it is driving but like I said as soon as my foots off that gas pedal it's dead. What could it be???????