Exhaust Gas Temperature (EGT) is measured in either the exhaust manifold or exhaust pipe. It is an indication of cylinder combustion temperature and will never be as high as actual combustion temperatures due to dissipation of heat into the cylinder head and pistons.
On diesels, a fuel rich burn will result in higher combustion temperatures. This is the opposite to petrol engines, where excess fuel is added under load and rather than being burnt, it evaporates and causes cooling, thus protecting the pistons and valves.
Back to diesels, cooling the compressed air charge, through intercooling, will result in a leaner (cooler) mixture can being achieved. From a performance perspective it means that the system can be pushed harder with more fuel being used to burn the extra oxygen.
An effective intercooler will reduce exhaust gas temperatures by over 100ºC and get within a few degrees of the ambient temperature. This means that critical engine components can operate at a safer condition while still under heavy load.
This reduction in combustion temperatures is extra heat that does not need to be removed through the radiator. As long as your cooling system is functioning correctly there should be no change through the fitment of a FMIC.