More observations - I've got ScanGauge now, so I can do more monitoring.
My oil cooler seems to be shot as I did see delta at 50+ degrees.
I guess the wrench-shaped light showing on my dashboard is indicating that, but the light triggers no code, so no firm confirmation.
But oil cooler beside, the coolant pressure seems to confirm what skanj0 tells >>> in extreme load the engine head has to lift and gasses enter the coolant.
Talking about my 15,000 lb, over 11 feet tall camper combo - the engine works close to extreme most of the time and speeding up 6000' elevations is not making it easier for sure.
Now having coolant pressure gauge and other gauges I could avoid a problem by backing my foot off the gas pedal when coolant pressure raise over 15psi.
Frankly I don't have to beat car traffic with my camper
but.... it gives nice kicks.
The delta stays below 30F on highway traffic, so the issue is only on high speed freeway climbing.
I use the truck only few times a year for camping, so rebuilding the engine is not an option for now, especially when I know I can avoid problems by driving slower than 70 mph.
What makes me thinking is that I drove the truck for over 600 miles before taking it for service at the dealer and putting the camper on it.
The problem did not exist than, so could the semi-synthetic oil dealer put in had something to do with it?
I have good experience with Rotella T6 that I prize for fixing high pressure pump leak and hard starts on my 7.3l. Maybe dumping the stuff dealer put in and refiling with T6 is valid option?