This is how I see it (and then I must get to bed!):
Theory. What you need to know is that high pressure air seeks out low pressure and that the highest pressure area on a car is the very front.
Just as air will try to skip round the sides of a car (and underneath and over the top), so it will try and skip round the sides of radiators, intercoolers and oil filters. You can force it to go where you want by building a baffle from the bumper to the sides of the rad (etc). The baffle needs some give in it or a small collision will take out the rad.
You can decrease the air pressure behind the rad by ducting air out: the vents on the Integrale, the Ford rally cars and the Elise/Elige are anything but cosmetic. Doing them properly, however, so they don't look like bits of plastic tat glued on is difficult: having them done professionally is expensive. In effect, these provide the air with a low pressure area it'll follow, and increase the air throughput. As turbocharging a car is pretty much about temperature control, it all helps.
A case in point, the oil cooler. Most (all?) turbo Cinqs have the oil cooler mounted on the extreme nearside of the car. Immediately behind that is the wheelarch liner. Vent that, just as on the offside of the Sei and you have a wonderful air extractor (the tyre spinning creates a super low pressure area). Box that all in with something like carbon or thin guage alloy sheet (do it right and it can be held on with velcro) so the air can't get confused and wander off somewhere else, then build a deformable structure out to the bumper. One less hot air source to worry about.