I have recently purchased a 1999 Ford Ranger 4 cyl, 5 spd with a/c and 65k miles. The truck seems to have a slight miss (slight bucking ) at higher rpm's like the timing is slightly off. The timing is not adjustable on this unit I understand. I installed new plugs and the wires will be next unless someone has an idea as to the problem.

 

First, welcome to FTE!!!!

Wires would be a good idea!! What kind of plugs did you install?
Hopefully you used Motorcraft, or Autolite double platinums.
Has the fuel filter been replaced?