Just FYI, "sugar in the gas tank" won't hurt engine, 20lbs of sugar could clog fuel pump/sock, but that's about it, old wife's tale, or "old mechanics tale", lol
Same with bleach, drain cleaner, ect.........
They actually tested alot of that stuff on a TV show called Myth Buster.
Yes, reads like your fuel pressure is low, changing filter brought it back up a bit but it was still low and so...........after a bit you are back to where you were.
'93 Ranger has a Return line fuel system, so 2 fuel lines.
There are two things that maintain fuel pressure(3 if you count fuel injectors)
1. Fuel pump, of course, is the source of the pressure, it has a check valve on it's outlet, to prevent fuel from running backwards when pump is off.
2. Fuel Pressure Regulator(FPR), this is located on the engines fuel rail, it will have a vacuum hose and the Return fuel line attached to it.
When engine is off the FPR has a spring on a valve that holds it closed so fuel pressure isn't lost going out on the fuel Return line.
When engine is running the vacuum pulls open the valve allowing fuel to flow back to the tank, when engine is idling vacuum is highest so more fuel goes back to tank, when accelerating vacuum drops so valve closes and less fuel flows back to tank.
'93 should have 35psi of pressure at the fuel rail, engine type doesn't matter.
35psi is alot, same as tire air pressure at 30psi.
On the fuel rail is a Schrader Valve, looks like a tires air valve.
The 35psi of pressure will stay in a working fuel system for many months, so it should always have lots of pressure.
Check it, but be careful, cold engine, press center pin down, fuel should squirt out 20-30ft, so be careful :)
You can also use a pressure gauge.
Check vacuum hose on FPR, if there is fuel in it then replace FPR, but they are very hard to test other than that.
The fuel pump is turned on by the Fuel Pump Relay, these relays can fail, but usually not intermittently.