2000 Nissan Sentra Service soon light on and acts like not

I replaced the fuel pump and noticed that the gas was returning to the tank just as fast as it was going in so I replaced the injector pressure regulator and it still acts like it is getting no gas if I pinch the return line to the tank it runs fine. I bought a Actron OBD 2 scanner and I get P030 Misfire detected changed spark plugs did not help P0171 too lean bank 1. I do not know if it is the injector or what.
On the Monitor it says
catalyst inc
oxygen sens mon inc
Oxygen sens ok
fuel System Mon ok
EGR ok
comp component ok
misfire ok
I have never noticed that the fuel pump works all the time when you start the motor but when you turn the key to get ready to start it pumps for a few seconds then stops but the minuet you crank the engine it pumps and the engine runs for a few seconds then dies and will not start till the pump stops
then start up for a few seconds like running out of gas.
It has plenty of pressure in the line.
I am stumped.