Welcome to Ranger-forums. There are some great How-to's here for mods that can be done to any rangers. For 2.3 specific stuff, you are welcome to check my webpage http://silvertank.batcave.net/index.html
since you are a 04+ I do not beleive that there is CAI that you can buy off the shelf and fit to your truck because the MAF is attached to the airbox, or something along those lines. while the peak gains from the tuners seem minimal it has been reported to make noticable gains due to the area under the curve. something that I have been interested in is the mazda 6 speed setup. It uses the same 2.3 as the ranger with a 9.5:1 compression ratio, and a turbo to output 274HP @ 5500 rpm and 280ftlb @ 3000 rpm... I dont think that there is a kit available yet, maybe someone with more knowledge will chime in. but knowing what marcy motorsports, cosworth and mazda speed have done with the duratec is comforting.