There are all kinds of things you can do for more power. Keep in mind it is a 4 cylinder so if you want a real boost in power your only options are turbo, nos, or just buy a V6 or a V8.
You can do headers, exhaust, intake, chip (depending on year), possibly a throttle body spacer, electric fan swap, coils, and a few others.
1998 Mazda B2500 Extra Cab 5sp manual
(1998 Ford Ranger 2.5 liter)
Cat back with Flowmaster
Headers (no name)
Power Aid TB spacer
JET Performance chip
Electric Fan coming soon!