Welcome to TRS
Reads like you bought someone else's problem.
I assume you did a road test before buying it so knew about some of the problems.
Engines are not to complicated, adding the electronics made them simpler and more reliable.
1991 Ranger will have 25 year old wiring and probably more than one owner that did "repairs" or added "stuff".
So really not to usual to have some problems.
On the upper intake toward the front will be the IAC(idle air control) Valve, all fuel injected engines need an IAC valve to set a stable idle, idle screws won't work, no Jets.
It is held in place by 2 bolts remove them and pull IAC Valve off the upper intake.
Have it's wires connected and turn on the key, it should open all the way, then unplug its wires and it should close, plug wires back in and it should open.
If not then use a volt meter to test Red wire to make sure it has 12volts(battery voltage) with key on, if so replace IAC valve.
Engine will barely idle with bad IAC Valve or will just stall, and will be hard to start, not enough air getting in
You were on the right track with FPR(fuel pressure regulator) if you smelled fuel.
Its vacuum hose was fuel free which is good.
Now there is the fuel injectors.
In the engine fuse box is the EEC relay, it powers the EEC(computer) but also the fuel pump Relay(not the pump) and it powers the fuel injectors.
When you turn on the key the fuel pump should run for 2 seconds then shut off, safety feature, it won't come on again until engine starts, or unless you turn off the key then turn it back on to get another 2 seconds.
So try this test.
Turn key off and on 3 times
Pull out EEC relay, shuts off fuel injectors
Crank engine, it should not fire if there is no fuel, spark is still on
If it does fire then there is a leak of fuel into intake.
Repeat test, but this time pull off the coil to cap wire so no spark
After cranking pull out each spark plug and check which one is wet with fuel, that will be the one with leaking injector.
You may be able to tell just by pulling spark plugs and looking for the darker plug, the one running rich.
Having CEL on but not being able to talk to computer could be a sign of computer failure, it is rare but not a never happens.
Since it is well past warranty, lol, you can open it up and have a look at the circuit board inside for signs of damage.
Good look here at what it should look like:
http://www.auto-diagnostics.info/ford_eec_iv
Not related to smelling fuel but important for 25 year old system, the TFI spark system.
Read here on troubleshooting this system:
http://www.therangerstation.com/tech_library/TFI_Diagnostic.shtml