I haven't done the math, but I can tell you from experience that it doesn't make the kind of difference those numbers indicate. I have a car with factory ram air, and I have run it at the drag strip with out the ram air and with it in place, and the difference is very very small, and then only felt at the end of the strip (I think this is where the ram effect begins to kick in). This leads me to believe that the difference is not temperature related. I also suspect that your estimate of under hood air temps is probably too high. It is very common to see wires rated at 85 degree C / 185 degrees F used under the hood with no problems. At idle the higher number is a possibility, but at speed, I don't know.... What I can tell you is the volume of air coming in through the front of the engine compartment, assisted by a fan in most cases, will swamp the air that might come through an open hood scoop.
Ram air and non Ram air cars (R code and Q code CJ) were both rated at the same horse power. On the one hand this might have been an insurance related thing (under rated) or it might have been that they just couldn't make the claim due to the way the tests were run (no ram air effect, no impact of under hood temps).
Finally, if you could really get the kind of boost that the numbers imply for basically free, you would think that this would be the first thing every engineer would design into the car. I have driven the same car at sea level and at 5000' feet and the difference is huge. Much bigger than any cold air / ram air induction system I have ever experienced.
Given all of that, it looks really cool. A new Camry will put most Cougars into the weeds anyway, so its getting to be less about speed and more about having fun, I say go with what makes you smile.