2.3l is a high RPM motor, RPMs need to be above 2,500 to have any power at all.
Check what axle ratio you have by looking here: Ford 7.5 & 8.8 Inch Axle Tag & Door Codes
3.73 was the "normal" ratio
4.10 gives better low-end and pulling power, but less MPG on highway
3.55 or lower is better for MPG on highway, but loses low-end power
4cyl rangers often came with the lower ratios, point of the 4cyl engine in a truck was MPG not power, so.............
Larger diameter tires lowers the axle ratio, stock tire size is on that door label
Google: ranger throttle cable mod
Many rangers no longer get full throttle because cable has stretched, easy fix for that.
If engine looses power at higher RPMs then change fuel filter, $10
Also get a vacuum gauge($25) and test for clogged exhaust system
Read here for tests: Technical Articles: Engine testing with a Vacuum Gauge - at Greg's Engine & Machine
Vacuum gauge can tell you ALOT about any gasoline engine, good tool to have.
A Lean mix will cause engine to ping/knock under load, always, so listen for that.