2006 Ford Expedition running poorly

I have a 2006 Ford expedition, new to me. Ran perfect no problems.  A
week later it would take a couple of times to start.  Took it to the mechanic
he said I lost fuel pressure when it shuts down, so they changed the fuel
pump. Didn't help changed it again.  Didn't help again and they upgraded
to a dealer OEM part. No improvement. We changed the fuel pressure
regulator still didn't fix it. Test and replaced all fuel injectors, ran fine last
night now it has a very rough idle and no power on acceleration. No codes
have shown up.  Planning on new plugs tomorrow, any suggestions or
places to check for potential problems.