Cooling problem, power problem...

[TruStang]

I have an 04 that has 102k miles on it. In the last 3 months it has developed a cooling system problem that has baffled me. the cooling system is building pressure so high that it pushes out of the degas bottle as steam. Its minute under normal load, but under high load/high boost there is a huge amount of coolant pushing out. Ideas?

Also I have noticed that the truck seems to be low on power, especially when towing. I tow a trailer to the dunes, 5k pounds, and the truck maxxes at 50 mph pulling a hill, 2% incline to 6% incline. i believe that i should be able to run up the hills no problem with only 5k on the trailer. Ideas?

The truck runs smooth, no codes, and without any signs of not running well. I am open to ideas that these issues could be related or totally separate.

Thanks for any input you can provide!