Very Strange Blow By situation...Rings??

[pwerwagn]

Here is the deal:
My truck uses no oil driving around town normally. I dont do a whole lot of freeway driving. I had never really made this connection but here are the symptoms:

Anything over 75 mph, empty, it uses about a gallon or so every 100 miles. It makes a royal mess of the tailgate, everything. Just a mess.
Right at 70mph, it will use about 2 quarts in 500 miles (found this out after a recent empty road trip).

Under 70mph empty, it uses none. Ive tried driving in 4th at like 60 (same rpm as 5th at 75+) and it doesnt do it then either. Only 70-75+mph, empty, in 5th.

The weird part: If I put anything behind it and load it, it goes away. I tried driving 90mph with the camper and boat for about 10 miles, expecting to have to clean the boat thouroghly, and none. Maybe a few specks on the trailer but thats it.
Even with just the boat (3500lbs or so), It pretty much goes away.
Yet empty, its horrible.

I had a vaccuum leak once, but found it after a lot of searching. There is a slight haze of smoke out the breather at idle, but you can only see it in sunlight.

With the increased load, the egts go up about 150* or so (even more with the camper on). Im curious if that is just enough heat to allow the pistons to expand enough seal better than when cooler?
I have not yet done a compression test, just making sure there isnt something im missing here.
FWIW, the motor has been pretty hot (EGT wise) quite a few times. 1800* or so, if not more.
It has around 180,000 miles on it.

Thanks for any insight,
-Jeff