intake air temperature sensor is probably bad. (don't remember what it is actually called)

what do you have in the way of tuning?

there are plenty of cars that drive around without a thermostat,
Does your engine get to operating temp?
while I do agree, that can cause issues since your operating temp is inconsistent, after letting the engine run for a while, and the block warming up, the entire system is heat soaked anyway and if the temperature isn't running away, then chances are, it is maintaining correct (or close enough to it) operating temps. If the problem is still there once it gets warmed up, then I would bet that the ECU doesn't know how hot, or in this case, cold the air is that is coming into the engine. It probably thinks that since the MAF sensor is getting colder, that more air is flowing in than it really is, and that is causing your problem.