I agree with the high vacuum, but wonder if it might be sucked in through the valve stem seals? These will see the full vacuum in the intake system. I had them get really bad on a car once, and at the end the car would go through a quart of oil in about 200 miles. Compression was just fine, and the exhaust gas density was in direct correlation to the instantaneous intake manifold vacuum.

Roger

Sounds like you do exactly what I do. When I'm due for a "clean" I drive in 2nd (auto) at full throttle @ 5500-6500 for as long as I can up the steepest hill I can find and then use the engine braking to slow down again (also using 1st when the speed's low enough). I've found this really heaps keep the engine running wels as well as sounding great.

As for the blowby, I thought blowby was when the oil got into the combustion chamber during normal driving (except WOT).

My best example of blowby is in my '76 244Dl with 700,000kms. when you hold it in 1st (auto) and take it to 6000rpm and then close the throttle, it blows HEAPS of smoke and then when I floor it again it blows even more smoke (I seem to have developed a habit of blowing smoke when ever there's a f*$% W*@#^! tail gating me......they don't come close to me again :)

The opposite of blowby would be suckby.

"I have recently started to downshift my automatic on a regular basis like I'm trying to kill it. I like to pretend I drive a manual. I also drive my car like a maniac, high revs and all. Personally, I think she likes it."

I have a friend who said he did that with his Ford Explorer. He just traded it in about a month ago on a new car, and he said it needed a new trans at just 89,000 miles. He also happened to get a car with a manual transmission. I would advise you to do the same. They're tons more fun than an auto!

You may be sucking some into the intake via the emission control system. Might not be a bad idea to clean the flame trap and associated plumbing.