2000 2.5l SOHC is the last year of the Ford Lima engines in Rangers, used since the first Ranger in 1983.
2.0l, 2.3l, 2.5l are all Lima engines made at Ford's Lima, Ohio engine plant, all used in Rangers over the years.
Replaced by 2.3l DOHC Duratec engine in 2001.
All fuel injected Rangers came with Cold Air Intake, air is pulled from in front of Rad Support.
Outside of a general tune up, which is pretty much just spark plugs these days, lol, there is not much for bolt on improvements.
Switching to an electric cooling fan for the rad will free up a few ponies and give better MPG as well, so win-win, Ford did this as well, not sure on 2000 through.
2.5l is a higher RPM engine, best torque is at 3,000rpm, so you do need to keep RPMs high to get best power curve.