Sorry, can't help with the Silverleaf part of it-- I would call them.
But am puzzled by several things:
You mention Caterpillar C-6. Suspect you have a Caterpillar 3126.
You mention exhaust temperatures of: "it ranges from 90 to 110, up to 120 on hard climbs) but at 1 time I saw it reach 150 degrees." That is WAY too cold for exhaust temperatures which run in the high triple digits and can go higher under hard climbs. I am not aware of any pyrometers that Caterpillar or Freightliner fit on RV's to be able to give you exhaust temperatures.
The 90-110 is WAY too cold for coolant temperatures, probably indicative of a bad thermostat(s). And 150 is way too hot for coolant temperature-- that is severe overheating.
So, first call is to Silverleaf to figure out exactly what you have.
And, tell us more about your: "I found that I was losing power to different circuits on the fuse panel under the dash." Certainly electronics will give bizarre readings with out of proper voltage range.
