I have the NACA ducts without the fan installed. My IAT1 (before turbo) and IAT2 (after intercooler) are always within 12-15 degrees of each other while moving/part throttle. After a hard run the IAT2 will climb but return to normal after a minute or two. The IAT2 temp will climb while sitting in traffic, maybe 20-25 degrees difference. I have never seen it above 135... I have the fan, but never installed it after Lonny advised against it. I have thought about it, but apparently if you place the fan in front of the radiator, you can inhibit the air flow (30% if I remember correctly). There is no room to mount it underneath, and very little wiggle room if mounted in the NACA ductwork.
I have recently added side scoops on both sides on the engine compartment. It would be very easy to mount another radiator near the gas filler area behind the scoop and possibly mount the fan on it behind the radiator. It would take minimal routing of the hoses to do so and it would double the cooling capacity. That coolent could be routed so that the front radiator feeds the back and cools on the second pass. I have the optional button panel around the instrument panel. The fan could be switched there on the "unused" switch like Lonny has his fan wired. The fan for the intercooler is loud, so I would switch it so I wouldn't hear it unless needed.
Food for thought...