need some help determining if its head gasket

[tb9555]

I purchased an 04 6.0 and recently started having the burping out the degas bottle with a little bit of white residue. It does it under load only. I put an inline pressure gauge on it (coolant) and ran the heck out of it. I put a new cap on the degas bottle before doing this. I started out cold and layed into it. The pressure didnt stayed between 2 and 4psi and then would drop off to 2 when i backed off. Did a few of those tests with a cold motor to get the same results. Once the motor was up to operating temps the pressure seemed real low. around 2psi driving. I brought the truck on the highway and layed into it hard to watch the gauge climb up to 18 burp and then drop around 14psi. I stayed on it for a little longer but the gauge didnt go up. I reached 70mph during that test. Once I back off the pressure drops quickly to 6 or 4psi. I monitored the gauge going up hills to watch it go up and burp and do the same things. I dont want it to be a head gasket but need someone to tell me to bend over and take it hard because that is what it is so I can stop living in denial and bend over. I was thinking about getting the AE program. Would that help pin point things? Thanks, for the help.