The 2.3 is just not a powerful motor in general. It's the smallest size they use in the Ranger. You could look into puttin a chip in it www.bamachips.com. Another good & fairly cheap power add on is gettin an electric fan. Instead of using the power from the motor to run the fan it gets the...
Headlight covers are definitely the cheaper alternative, but the black headlights look a lot cleaner & they don't make it hard to see at night with your lights on lol. What color truck do you have?
Could be a number of things. You may want to consider the MAF sensor, thermostat, plug wires, & fuel filter. Those are just general guesses but it does sound like it's somethin along those lines