What is the purpose of running air from the turbo through a radiator-like-device in front of the truck prior to going into the intake manifold?

 

Welcome to the DTR. That radiator thing is actually an Intercooler. It cools the air that leaves the turbo thus cooler air enters the motor and WHA LA, cool air helps your engine and turbo operate more efficiently.

 

Not to be to picky but...it actually cools the air that is LEAVING the turbo, not entering the turbo. Cool air is more dense - resulting in more oxygen molocules in the combustion charge, resulting in more power..thus the intercooler - to make more power.