he's limited on air intakes with a 2004. No Mac available. The revised MAF sensor made it a little more difficult so a lot of manufacturers haven't made one (yet)
Dan, underdive pulley will get you better mileage plus 8hp. For $100 and an hours work it's a great value.
E-fans are touted as a mpg gain by a lot of folks.
The tuner will help also. You can tune for economy (mileage), performance (HP) or towing (torque) within a range of octanes.
Roller Rockers for the 3.0 Ranger. The fact that they exist for a 3.0 is just...cool. Had to mention them. No mileage gains though.
One thing to keep in mind- exhaust and intake is gonna add noise. Its nice to have one quiet vehicle. I'm sure the stang has a nice rumble to it.
2004 Ford Ranger Sonic Blue 4dr 4x4 4.0 Manual