I have always installed the winter cover on my GM's when it is below 30f. It gets plugged in when below 0f. A good friend of mine bought 2 new 6.7 Fords this year and had the cold problem too. He was plugging in...but the trucks would still run cold for about 30min. He ended up getting a couple of winter covers and it solved the problem.
As far as making no boost. We have an 8l Cummins in a box truck that does that too until it reaches normal operating temp...180ish. I think it is part of the "engine protection" feature.