1992 Pontiac Grand Am Car stalls out after running for 20 m

Hello I have a strange issue with this Grand Am. You can drive the car for about 20 to 30 min and then it starts running rough and dies. It will not start again unless you let it sit for about twenty minutes. I thought fuel pump but it has a constant amount of fuel pressure around 40 psi when running and when cranking after it has died. I found that when it has died the injectors are not receiving power to them. Also if you run the car for about twenty minutes and it doesn't die you can shut it off and restart it fine but if you let it sit for a few minutes and try to start it it will not start. I also was able to run the car on starting fluid sprayed through the intake during a period when it was not starting. I am fairly certain it is the injectors not pushing fuel but I am not sure what would be causing this?