Flashing Check Engine LIght/Low Fuel Pressure

Hello. I have a 1996 Nissan Altima GXE with a manual transmission. It currently has 192,000 miles. I have owned it for 17 and a half years. About 6 months ago I began noticing that the check engine light would flash randomly while I was driving. I never though anything of it and drove it like that for a month or two. After that, the car would begin stalling while driving at any speed. Sometimes it shut off completely on the expressway. Luckily, I wasn't in an accident. The flashing check engine light continued and from my nissan forum some suggested that I had an intake leak. Later the car would start normally and drive normally, still with the flashing check engine light. I would then stop somewhere and upon my return the car would really have a lot of trouble starting. Many suggested that I replace the intake manifold gasket as a repair. I did. It didn't fix anything. I then installed a fuel pressure gauge in my engine bay and monitored it. Well, in the morning when the car is cool, I get normal fuel pressure as per the Nissan repair manual. A few minutes of driving the check engine starts blinking and upon pulling over and opening the hood, I notice the fuel pressure at 20psi, when it is supposed to be at 32-34 psi at idle. Mechanic sees this and has me replaced the fuel pump. I replaced it with an OEM Nissan fuel pump with a new strainer and new filter before the fuel rail along with a new fuel pressure regulator. I though since the car is 21 years old, it wouldn't hurt. It still does the same thing. There are no fault codes of any kind. I haven't had any. I have an Actron Scanner 9145 I think that let's me look at live date. I think the low fuel pressure is the reason I have all the problems. But would that cause the MIL to blink randomly? New fuel pump, but still low fuel pressure? I would greatly appreciate any comments that would lead me to a final repair. Thanks.

I with a randomly flashing MIL and no fault code generally my first reaction is it is caused by a misfire. The cause is most likely your low fuel pressure.

I would start by doing a very simple check when the symptoms occur revmove the fuel filler cap to release any vacuum build up in the tank and see if the fuel pressure returns . Another suspect is loose debris (usually paint flakes) floating covering the inlet strainer but I think you would have noticed when you changed the pump.
The main suspect must be either low voltage at the fuel pump or a poor ground at the pump.

Thank you Andy. I didn't notice any paint flakes when I changed the pump. My car has a plastic tank and I'm not sure if it is painted inside. But perhaps I should have taken the tank off and cleaned with something. There were no debris of any kind when I emptied it and installed the new pump. I did fill the tank back up with fuel before I primed the new pump that included a new strainer. As far as the fuel filler camp removal, do you mean remove it when I get the low fuel pressure with the engine running? Or stop the engine, remove the fuel filler cap, let it vent, reinstall and try again and check for different fuel pressure? I am not a great vehicle electrician, but I do understand most of the concepts. I was trying to test the relay when the symptoms happen (low fuel pressure and hard starting along with the blinking MIL) and I didn't know how. I removed the relay and tested, and it tested fine. Although I didn't do it immediately when all the failures happened. I let the car cool down before I tested the relay. It worked fine, clicking and having continuity only when battery voltage reached the coil leads of the relay. I did notice something though. My battery registered 12.42V and when I put the key ON to check the voltage at the harness of the relay, it showed 11.99V. Is it common to have a voltage drop of 430mV? It seems excessive to me, like there must be something causing a high resistance. One more thing, how would I go about checking voltage and ground at the fuel pump?