D16 low oil pressure when going up big hills

what is the oil pressure on idle. last time i looked at a truck that they messed up the engine brake o rings it was sitting at 30 psi when cold on idle but something is definately wrong if your truck is shutting off this would be a good starting point to check these o rings, people mess up all the time when putting them back it's happened to me a couple of times to. 55 is to low on high idle which is what im assuming you're describing last one i saw was at around 90 ive also seen them at 65 which is still ok

 

check the o rings for sure

 

oil temp is relative to coolant but i have never seen it over 250 maybe 240 tops

 

I would check sensor I believe your oil temp sensor and coolant are the same sawp them and see

 

check sensor spray ratpiss in plug it sounds mostly like you need to do big ends and mains