You have the problem of radiant heat transfer Ian, thatll heat the intake up regardless of the airflowing past as its got line of sight to the hot exhaust.
Id suggest if you placed a temperature probe on the surface of the intake in proximity to exhaust manifold, youd see some very high temperatures being transmitted.
The airflowing over the two parts will obviously transfer some heat away as the intake absorbs it but when you have line of sight in such close proximity that effects going to be small in comparison to the temperatures transmitted.
Itd be a bit like grilling your toast and blowing cold air over it- the toast still gets done due to the radiant heat.
The other heat issue is the exhaust gases as they travel through the ports and heat the surrounding material, which is transmitted to the intake via conduction.
Anything you can do to drop intake temps will show up in cooler charge temps, which means you get a denser charge and a bigger bang for the buck.
At the end of the day, experimentations going to determine a win or lose situation on this question i think .
