I have a 91 firebird v6 3.1, it runs good when I first start the car but after it warms up it starts running bad and then dies. Any ideas?

fuel pump? Check fuel pressure.

could be coolant temp related? closed loop issue?

check the ohms on the injectors hot and cold.

I checked the fuel presure and it was 5psi, checked the filter and it is new and clear.
Now it will only run real bad all the time so I think it's the fuel pump.