Welcome to the forum.
Just to be clear.
When you turn on the Key the CEL(check engine light) comes on, and then goes off after engine starts, so you know CEL is working.
And you checked for codes in memory and none were found
You didn't mention cold and warm so.......
Engine runs fine at all RPMs when cold
After it warms up it idles fine, under 850 RPMs
Above 1,000RPMs it starts to run rough, and then smooths out above 2,000RPMs
I have read that 2000-2001 3.0l Coil packs had problems, but that should cause a code on spark feedback and misfire.
Compression issue should set misfire code
Fuel pressure wouldn't, 2000 Ranger should have fuel pressure between 60-70psi when running and drop to no more than 45-50psi when shut off, and hold that pressure for weeks.
There is a pressure fitting on the fuel rail, looks like a tires air valve because that is what it is, a schrader valve, and works the same way.
Testing fuel pressure can tell you of lower pressure than needed but also if a fuel injector may be sticking open, causing rich condition.
You mentioned spark plug tips with fuel on them..................