giving it gas and rpms freeze

[mikenissan08]

i've put a 92 motor in my 91 hatch cuz my head was trash and i've put a new starter back in and my car turns on fine and stays running. i've tried giving it a little gas to see if i'd get a response and the rpms freeze then go down when i let off. then it goes back up with no back fire. if i keep doing it, it then turns off. so i took out all the fuel injectors and the car was still running. one of my friends say it's the fuel pressure regulator i put all the small vacuum hoses on the back of the motor on myself. maybe the one that connects to the fuel rail is wrong. can anyone help??