I have replaced or updated the hpop fitting and also the standpipes in the heads and not sure if it goes with the problem at hand but I am losing coolant also not sure where it is going but seems to be low after every time I drive it ?
The hard-to-start-hot pretty much nails the fact that one of your problems are oil delivery related (in the HPO system). Standpipes, dummyplugs and for the year, the STC fitting are the usual suspects..however not the only ones. The air-test is the only way to nail down where the leak is.
For the loss of coolant, that is probably a failed Oil cooler AND a failed EGR cooler.
The oil cooler is a liquid/liquid style cooler. The coolant flows through to pull the heat out of the hot oil. The design of the oil cooler is such that any garbage that is in the coolant will stick in the oil cooler. Over time the amount of garbage in the coolant passages of the oil cooler slows the coolant flow. The EGR cooler gets its coolant flow directly from the oil cooler. Slower moving coolant and the high temperatures that the EGR cooler encounters quickly lead to a failure. The EGR cooler cracks internally and begins to leak coolant. When the EGR valve is closed, the coolant will flow into the exhaust, up through the turbo and out the exhaust pipe as steam or liquid.
To check your EGR cooler for leaking, park the truck on a decline. Pop the EGR valve out. If the soot on the EGR valve or in the intake is anything other than a dry packed powder, your EGR cooler is gone. If you can't determine that, leave the truck like this overnight and check the bottom of the hole for the presence of moisture.
If you replace just the EGR cooler, you reacted to a symptom and have not addressed the underlying cause. A new EGR cooler will not last long unless the oil cooler is replaced at the same time.
This is the failure that has given the 6.0 it bad reputation. The coolant flowing from the failed egr cooler leaks into the intake manifold, into the combustion chambers and pops the head gaskets. You will need to pressure test the cooling system to determine whether or not your head gaskets have been compromised.