Well you could check all the engine and chassis grounds. The computer hates bad grounds. It won't get enough voltage (or to large a voltage drop) and therefore attached sensors will not funtion properly. This includes fuel injectors. This could cause it to lean out and cause the high temp, detonation and lack of power. Sounds crazy? I had it happen to me. The engine to chassis ground was bad and the car was ok for about 30 min of driving. Then things would get bad. Detonation, high temps.... it sucked.
This is just another idea that seems to fit your symptoms. Hey, if you feel like just add a couple more ground lines to the block, chassis, alternator and battery. The more the merry.
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