Got some codes....

[SuperCrutyPS]

Here's the scenario. It's happened a couple of times now, but only when I've got my 5th wheel (~12K) hooked up and climbing a long steep grade (7-10%). RPM's are up in the 2500 - 2800 range. Boost is up around 18-20. I try to keep the EGTs around 1200-1250, but have gone as high as 1400 for a short time. It lights the SES light.
If I'm daily driving the truck and I go WOT, it will not light the SES light. But....I'm on a flat road, not on the same grades as when I'm pulling.

Here's the codes and what they say they mean:
P1211 - ICP pressure above/below desired - IPR valve failed, stuck, or shorted to ground
P1249 - Waste gate steady state failure - GND short, plugged hose/port, solenoid, actuator

On the ICP, I'm not very familiar with this. I see the cause says the IPR valve failed, etc. I'm making the asssumption that one feeds the other information. Is this correct or am I missing it altogether?
On the WG failure, is the solenoid starting to crap out?

Any information will help and is much appreicated.