my 3 month old purchase has run 'intermitently' hot, never up to the red on the dial, since I bought it.

-Replaced the thermostat and coolant to no effect. top hose is hot

-Running the heater in the cab helped bring the temp down (sometimes). This made me think that it was probably not a faulty temp guage.

-Checked the radiator after warmed and it felt much hotter at the top where hot coolant comes in from the engine, though not neccesarily cool at the bottom. I went ahead and bought a new radiator and hoses -plan to install this weekend.

I opened the air box on a mild day and found that the preheat shutter valve was open to the hot air intake. The bently says that this valve should be in the "full cold position" at above 59 F. I used the girlfriend's hair dryer to heat the therm up, and it did fully close the hot air intake, but at that point it was really hot. So I pulled it apart, and replaced the thermostat with a bolt and nut assembly to force the shutter valve to always close the hot air intake. (found this solution on the brickboard) This seems to have solved the overheating problem.

Now I am wondering:
1. how i would know if the AMM has been damaged by the hot air? The hose after the amm to the throtle body was brittle and had holes so I replaced it.

2. Should I replace this thermostat as I will be driving in cold weather in the winter? I would prefer to not screw with the emissions control devices. Where can I get a new one?

3. Am I overlooking something else?

thanks all,
nathan