Lately when I start my G8 on cold mornings it shutters and almost stalls. The colder the temp, the worse the shutter is but after about 10 to 20 seconds it goes back to a normal idle and runs fine. I had read it might be the IAT and MAF so I hooked my scanner up to it, the IAT stays at 32°F regardless of how long its been running. However another function on the scanner is power- up IAT, and that one will gradually go up as I drive and the engine heats up. I'm curious as to what the difference is between the IAT and power-up IAT, if my IAT is actually bad, and what would most likely be causing this issue. Also my fuel economy seems to be suffering.