Engine dies

I replaced tps and iac already new plugs all coils and injectors firing when I put the car into any gear it dies I know what you're going to say torque converter locked up but if I give it to stuff like that I guess it doesn't die it's idling at like 400 and neutral the minute you put it in drive the idle drops and dies if you turn on headlights the idle drops significantly if you roll the window up the idle drops significantly if you turn the heater on it almost kills it I haven't had my alternator tested yet but could this be causing all my problems even the dying when put in drive