... I've been having intermittant fuel starvation problems to the point I don't want to risk driving anywhere. The car dies as if running out of gas while cruising. As a result, I replaced the fuel filter and added some Lucas fuel system cleaner (thinking I might have gotten some bad gas or water in the tank) but with no improvement.

Basically, the RPMs would dip while cruising just like running out of gas then resumes. From OFF, it usually starts right up, but almost immediately dies, or dies after idling for a brief period. Then sometimes, it'll run fine 'til I shut it off.
[list][*] I can hear the pump prime and I believe it runs while the car is running. I can hear and feel the fuel pump relay working.[*] If I watch the injectors with the car idling, they're fine for a bit, then stop (I see the spray stop), where the car dies.[*] I disconnected the fuel pump relay and started the car, and it ran, so I know the oil pressure switch works.[*] I pulled the codes, and got a 23, and a 42, which led me to check what I checked.
After I disconnected the FP relay, I got a 54 (obviously).[*] I disconnected the MSD and ran the stock ignition with the same problems.

What am I missing in my troubleshooting here?

Someone please help! This is the first time in my car's 12 year life that it's been completely disabled like this, and it sucks!

 

Well its obvious that you are getting fuel, but are you getting enough pressure. Check the fuel pressure, as you may have a weak fuel pump.

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Rob
'86 TA 305 TPI
Gutted MAF
Ported Plenum
TB Bypass

 

Sounds like the pump itself may be at the end of its useful service life...

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"So many Mustangs, so little time..."
ICON Motorsports