This could work. To do it properly have the fan controlled by a temp reading from inside the TMIC.
Testing to see if it works would be a challenge in getting identical conditions, dyno results would not be meaningful.
On the other hand, a TMIC water spray setup may be simpler. Water has a much higher specific heat than air so the volume of water to do the job would be much less than the volume of air.

What kind of conditions do you have to want a performance improvement? -see comments above by Hurtenstein and Jacob92. If you drive in hot weather in heavy traffic, then require full power/torque, or say after a long wait at traffic lights on a hot day and you are in front, then this is what you could try.

Another thought, 400whp, 300kw atw, from a GC8, a good target, it would be at 5000 to 6000 or more rpm when moving at a fair rate. I doubt that the ProcessWest TMIC is the limitation. What turbo will you use?