91 firebird v6 please help

i have a 91 bird when you try and start it it floods itself out it dont do it all the time sometimes it starts real fast got a new pump new plugs cap and rotor new wires when it wont start i can pinch off the fuel line and it will start right up does anyone know please help

i also have a 91 bird with the v6, have never seen anything like that. only thing that comes to mind is injectors stuck open, but all six stuck open dont sound right. they usualy wont go bad all at the same time. something i use in mine is SEAFOAM. a bit pricy but works pretty good. it cleans out the fuel system, oil, and air system. just follow the instructions on the can. hope i got ya in the ballpark.