I did some tests on mine to see if I could get it to "run hot". I've had it out in 102 heat, with the air on, in traffic, and it would not overheat. I would not worry about the tempurare as long as it does not overheat (also, make sure the fan comes in of course).
Regarding losing power, this is probably the engine management system retarding the timing and/or fuel mixture. When the fuel reaches a high enough temperature on a really hot day (or, if you get a tank of gas that is of lower octane than usual), then you may notice a slight loss of power. This is done to protect the engine.
Mine had a little power loss on a real hot day here in the summer, which coincided with the first time I used Chevron gas (91 octant of course, but who knows how accurate of an octane you really get these days). Anyway, the car lost a little power (not much; just enough for me to notice when I hit it real hard). About 2 tanks later (a week), it was back to normal. The weather was back down in the 90s and I stopped using Chevron. I have no idea if Chevron gas had anything to do with it...I think it was really just because of the 102 heat making the fuel temp too high.
One important note: the fuel temp is not related to engine temp, so even if you're engine is running hot the fuel temp will probably still be under the threshold needed for the engine management system to kick in. I think it's only on rare occasions (like a very hot day) that the threshold would be met. And, if the threshold is met then it's not a problem because the system will "re-learn" and go back to normal as the conditions improve (lower fuel temp and/or better fuel).
