Calling all old schoolers.......

Go to harbor freight buy a fuel injection pressure test kit.
There should be a schrader valve on the fuel rail.
Put the gauge on the schrader valve and drive it while being able to see the gauge.
When it quits get back to me here with what the pressure reading is.
Doing a fuel pressure test at idle is not conclusive.
Also when you have the gauge on it at idle and you jog the throttle pedal fuel pressure should rise.
And Also at idle if you pull the vacuum line off the pressure regulator
(Which should be located on the fuel rail) it should rise to maximum pressure.

 

FYI
Fuel pressure for that engine should be 35-40 psi with a significant rise when you step on the throttle.
Looks like you are a little low to start with.
If your pressure checks out then you may need to move on to a fuel flow test.

 

I was a ford master tech back during that time, sounds like maybe a fuel pump, some of those had a pusher pump on the rail under the drivers door with 1 in the tank or it could just be a dirty fuel filter, also the relays at the air filter could be weak,1 is the [eec] relay,1 is the fuel pump relay, replacing them every couple years is a good thing along with 2 in the glove box

 

You need to check the pressure when it’s failing not at idle

 

Lots of good suggestions here. X2 on something in fuel tank.

 

I probably should not comment but you almost put my name on it.
One of the shops I was over did mostly diesels. A mechanic , that was very good, had already informed me that I am a dinosaur mechanic. " If it's not a dinosaur you do not know how to work on it. "
I pulled a Ford in the shop and opened the hood. I was amazed they put 7.0 on the grill and all that electronic crap on a perfectly good 429. While I stood in wonder mister smart butt walked up. " What's the matter boss? To new for ya? " I did not answer but he was correct.
Buddy and some others pretty much covered everything but I did not see the tank vent mentioned. Check that and or run it with the cap loose.
Need a pressure gauge on it so you can see what it is doing while you have a problem.
Maybe not much help from here but maybe you got your laugh for the day.