In an effort to reduce exhaust emissions 1995 and up(EEC-V, OBDII) Rangers with manual trans will hold RPMs above 1,200 when clutch pedal is in, they shouldn't go up but they should hold the RPMs engine is at when clutch pedal goes in, after 5-15 seconds, with pedal still in, the RPMs should start dropping to 1,200 and then stay there until speedometer is below 5MPH, then RPMs should drop to 650-700, normal warmed up engine idle for manual trans.
Now there were some issues in the early 2000's about 3.0l computer software that caused this increasing RPM issue, it required Ford Dealer to reprogram computer.
TPS is pretty simple to test with a voltmeter.
Set meter for DC Volts
Key on engine off
Use a sewing pin to pierce the TPS's center wire.
Meters black probe goes to a ground
Meters red probe goes to the pin.
TPS voltage should be under 1volt when throttle is closed, .6-.9volts is spec
At wide open throttle voltage should be above 4.6volts
What you are looking for is a jumping around of voltage while you slowly open and close throttle, voltage should steadily increase or decrease as you open and close throttle.
If you see volts dropping or jumping up, then you have a bad TPS.
When you press the clutch in you are removing a load from the engine, so if gas pedal is not released then RPMs would go up.
So other reasons are a sticking throttle or Cruise control cable, weak Throttle spring.
Even carbon build up in throttle passage.