So I am running the MSD pump. Putting out about 50 psi through the areomotive regulator.
Return style. About a 5/16th return with a 3/8 pickup.

Powering a magnum 5.9.
Went to see christmas lights in the convertible, so we were idling around with my foot on the brake for about an hour.

As I went to make a left, the car started to idle funny and eventually died.

I had to push it to the side of the road. No matter what I did, it wouldn't idle or stay running.

I popped the hood thinking a burned out wire or something, but no check engine light so not a bad sensor.

I noticed the fuel pressure gauge read 20 instead of 50.
So I turned the key on and it stayed at 20.

I broke out a pair of plyers and got it to turn the adjuster to where it was almosted bottomed out, but never got more than 20 psi.

Called up feets to come get me and messed with it another 10 min or so and noticed the gauge creaping up to 40 psi.

Turned the key and it hit 60. Fired up the car. Got the kids back in and managed to drive it home sitting on 60psi the whole time.

Got home turned it down and it still seems to be fine.

The regulator held 20, the pump made noise, but maybe it over heated? It is a return style regulator, and I had almost a full tank of gas.

I know the gauge will read 0, so it is good.

Any idea where to start on this?

How close is your pump to a heat source like the exhaust?

Clogged pickup? Ice?

Sounds like your regulator got stuck in full return mode, just a big ol dump back to the tank. When the pressure slowly started to build, the regulator spring or whatever it uses was starting to neck down the return thus building pressure. I would look at the regulator for starters. Did you notice the pump frequency change during the "healing" process? It would be difficult to know whether the pump was the culprit or the regulator but if the pump was floundering while you had 20, that would be the pump. It should have been going pretty good at 20 if it were the regulator.

Regulator stuck possibly but it may also be the pump getting hot and starting to fail. I had a similar problem with an external EFI pump. When everything cooled off it worked. Replaced the pump and it kept working. Cavitation and heat will kill the pump. I was fighting cavitation.

I've concluded the external pump and factory style pickup for EFI isn't the best setup. I'll probably sump the tank or get a tank with the fuel pump inside. I don't like coming home on a flatbed.

the pump is mounted to the frame rail, so I would guess maybe 5 inches give or take.

It was 70 degrees out. So no ice. Cool enough I had the heater going with the top down.

I know that when I let the car sit, the gauge will go to zero. When I first installed it, the regulator would hold 50 psi for about 3 days.
Lately it will drop to 0 after sitting a few min, and sometimes it will hold for an hour, but rarely more than that.
Bad reg?

The pump was still making noise, but I was in a bit of a loud area, and all I could tell was it was running. Didn't sound different, but it was hard to tell. If anything it was quiter then I remember, but I was near trafic so hard to tell.
The efi system auto shuts it down after 3 sec without start up.