The factory gauge is an on/off switch at 6 psi, it doesn't tell you anything except that you have SOME oil pressure. If its flaking out it could be the gauge or wiring or the sender. Best way to tell if you are having issues with the oiling system is to install a legit aftermarket gauge.
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.