Why don't the 6.0's ever really heat up to operating temp without EGR and with it takes them forever? I know Diesels are cold blooded but still. Mines takes 10 minutes at 1200 RPM to get damn close and even then T-stat isn't open....
Ford designed the cooling system with the EGR. The EGR puts a TON of heat in the cooling system even during normal, unloaded running around town. So that had to be taken into account with the cooling system. I know on mine, before the EGR Delete, if I really got on it on an on-ramp you could feel the air temperature increase when I had the hammer down.
Now, remove all that exhaust heat, and the cooling system has the upper hand, now that it has much more cooling capacity than a deleted 6.0 can produce. I know with mine. I work ~30 miles from home. I park in a parking garage, that is open-air and the same temperature outside. If its in the teens, I can start the truck, drive home on the interstate and county roads (50-70+ MPH). I can stop at the gas station near my house, leave it idle and lock the truck. When I come back out ~5 minutes later, it will be on high idle, since the coolant is not at normal temperature. Now, if it's in the 20's or higher, it's not so bad.
It's not just with the 6.0. A coworker has a Duramax, and it's been deleted also. He made a comment last week when it was near 0, it was warmer in the truck than outside, but it was no where near "room temperature" warm.