Not really much of a step by step Brett -- I extended the harness as you're suggesting and relocated mine to the elbow just upstream of the throttle body. Air box will work too. Just do a little measuring so you know how much to extend the harness by; do one wire at a time so you don't get them mixed up; solder/shrink wrap the connections; I bought (cheap) replacement plastic loom so it looks factory. I found the right size bushing at Home depot so the ACT will screw into it; and I drilled a hole/used some JB Weld as thread sealer to screw the bushing into the elbow.
See the pic -- look just upstream of the throttle body and you'll see the ACT sticking out towards the firewall; small heat shield under it I fabricated to keep heat from the header off of the ACT.
Richker has a neat approach removing the specific wires from the salt/pepper shakers and lengthening them from there so that there are no splices. I found it easier to simply lengthen the harness - and properly soldered/wrapped splices are no cause for concern.
I would do the same too...just lengthen the wires and route it nice. you could drill and tap the hole where its suppose to go in lower if you wanted too(on a fox anyways)...from what ive seen its just a nice flat surface....in one thread i think Tmoss posted the exact drill bit and tap you would need
Andy - it depends on which lower you have as to whether the boss is there or not; on the later model Explorer lowers (later 97 on) without internal egr, there is no boss. Anytime I have a reasonable alternative that will allow me to avoid trying to drill and tap an aluminum casting without a boss, I take advanatage of it. If mine had come with the boss, I probably would've located it in the stock position - #5 runner.
The ACT (Air Charge Temp) sensor will probably need to be moved. The GT 40 manifold isn't drilled & tapped for it to go into the intake like the stock manifold was. There is a boss cast into the GT 40, but a machine shop will have to drill & tap the new manifold. The best spot for the ACT is the air box if you don't do the drill and tap thing. You get to cut and splice the 2 ACT wires in order to make them long enough to reach the air box. Solder the wire extensions on the existing wires & use heat shrink tubing to cover the splices. Offset the place where you cut the wires so that you don't have a big bulge when you put heat shrink over the 2 wires to cover & protect them. The stock air box gets a hole (5/8" or so) for the ACT drilled about 1 1/4" down & 1/1/4" in on the front top side near the upper radiator hose. A brass fitting nut from Home Depot or Ace Hardware secures the ACT into the air box.
If you are very clever, you will find that the ACT connector comes apart so that you can remove the pins. A very small screwdriver releases the lock in the front of the center insert, while another small screwdriver inserted in the back pushes it out. Once the center insert is out of the connector shell, the pins come out easily. New pins are available from AutoZone in a $5 electrical pin kit for Fords. Crimping the pins on the extender wires saves you from having to splice them twice: once to put the connector on and once to extend the wires.
6 ft black 18 gauge wire
6 ft green 18 gauge wire
6 ft 1/4" heat shrink tubing
1 ft 3/16" heat shrink tubing