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You also need to check the power to the relay during ignition on. Check for the 2 second run and the continuous ignition power. If those are not getting power, it is the ECU or the wires to the pump. I had a switch on the Jimmy that ran the pump contiguous when the relay died on the trail one year. Shut it off manually. You could try that to make sure the pump wiring is not the issue.
I know you said the pump was new, but running well then stall wait 20 mins to run again always says to me bad pump. What brand and where was pump sourced.
Hot relay and wiring can also point to a pump failing
If you don't have a skid plate under tank. Next time it stalls and won't restart right away, give the tank in the area of the pump a few light raps with a soft face hammer, or dead blow. Then try it again, if it starts I'm going to go out on limb and say that fuel pump is failing.