I have a 1993 ford taurus 3.8L V6 automatic GL. My problem is that when it gets very hot and humid my car will stall. I hooked up a fuel pressure gauge when it stalled and the fuel pressure read below 20. I let it cool off for about an hour and the fuel pressure read 35-40. What in my fuel system is failing because of the heat? Is it the fuel pump, fuel pressure regulator, fuel injectors or what?

. Change fuel filter.

. Check fuel regulator.

If the problem persists, then focus on the fuel pump.

Another possibility is vapor lock from poor fuel line routeing. You may have to insulate the lines and/or create a heat shield around them.