2011 ecoboost that after driving and then turning off for 20 to 45 minutes the truck would start but very rough idle than die. Would take 4 to 5 tries to get the truck to start properly. Check engine light comes on and the code said "low fuel rail pressure" code reader show the fuel pressure was only 20 PSI. Dealership replace the high pressure fuel pump and that only made the problem worse. Runs fine when the pressure is correct but that takes multiple tries starting it. What else could it be?

 

Assuming that they replaced the fuel filter (or at least checked it) ...

Fuel pressure regulator.
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Any chance you got this sorted out? I have the exact same issue and I dont want to just start guessing and replacing parts!