I recently (a week or so ago?) completed my own similar setup. I used the parts from Modshack's original DIY (the fang flanges, mounted the same way, and the same hoses), but I did the hose routing basically like the pics in cotizi's top post here (around the sides), and brought the ends of my hoses up to where they're even with the backs of the Gen 3 filters. I used some long plastic zip-ties at the ends and a couple places along the middle to keep everything in place.
I monitor my temps (Ambient, Oil, Coolant, Intake) pretty religiously all the time. I have my cellphone docked in my cubby w/ the door removed, and run
Torque on that to monitor the coolant/intake temps, among other things.
The simple summary of the IAT changes is this: at highway-ish speeds (60+) it makes only a tiny difference, and I doubt it's enough to make up for the aero losses opening up the fangs. However, at slower rolling speeds it's actually really effective.
Prior to hooking up the ducting, I was generally observing a +12-13F IAT (over Ambient*** reading) at highway cruising speeds, and ramping up pretty quickly at slower speeds (not uncommon to see +30 or more at speeds under 30-35mph, depending on weather and traffic). With the ducting the highway is about +9-12 now, but at lower speeds I'm never more than +20-25 worst case (e.g. 10mph in traffic for a while). In general the IATs drop off a lot faster now as I accelerate, and stay lower longer as I decelerate as well.
I assume the minimal difference at highway speeds is because at those airflow rates the default Stillen setup was already getting all the air it could use through the main front grill. At lower speeds though, the ducted fresh air displaces some of the radiant hot air we'd otherwise be drawing off the top side of the radiator.
My net take on it is that it's definitely worth it for city driving and the track. Especially in a track scenario on a hard corner, I imagine it could save you 10 more degrees on your IAT at the moment you're starting to accel out of the corner, which is when you really want it the most. On a highway road trip it probably just eats MPG via aero losses for tiny gains though. Be nice to find a way to plug them for a roadtrip, might not be that hard to figure out.
*** - Keep in mind that our Ambient temp sensor is pretty useless in the absolute sense: they get road dust, dirt, and fluids splashed on them, they're not terribly responsive, and their relationship to the true ambient temp (vs coolant/oil temps) varies with other changes in the airflow/heat configuration under the bumper (coolers, etc).