Cheap and good to have tools are a vacuum gauge, and a volt/ohm meter.
Read here on using vacuum gauge:
Technical Articles: Engine testing with a Vacuum Gauge - at Greg's Engine & Machine
No matter what they do to the outside of an engine it is still just a big air pump, which is why the vacuum gauge is so handy :)
The added electronics have made the engines much more reliable, the volt/ohm meter allows you to test the electronics if there ever is a problem.
And "don't shoot the messenger", if you ever get a "trouble code", check engine light(CEL) comes on, it doesn't mean a sensor is bad, it usually means a sensor is good and detected a problem, lol.
Many people waste money on replacing sensors and controls because of a CEL, when all they had was a vacuum leak or loose wire, $25 volt/ohm meter can save you hundreds of dollars in parts.
Vacuum leaks are common issues that can cause all sorts of problems, the ford vacuum hoses start cracking after 10 years or so, so if you have a vehicle over 10 years old and have a rough idle or loss of power, start with the larger vacuum hoses, PCV valve hoses are notorious for leaking on Rangers.
This is where a vacuum gauge can come in handy, with engine running good you should check engine vacuum when cold and then when warmed up, write down the RPM and Vacuum number for both cold and warm tests, put paper in the glove box.
If you start to have a problem you have a baseline you can compare current vacuum readings to.
Yes, it is not Rocket Science, lol, but the more "they" make something fool proof, the faster "we" make a better fool, "we" will ALWAYS win that battle