Good points from George, Rhys and Phil. I recently worked on a car with a Weber and the carb was coated with oil as it was spilling out over the filter. Turned out to be a spongy vacuum line from side breather to manifold that colapsed at idle making the top vacuum hose (from cap to filter) suck oil.
Just a thought,
Shayne.

Pull the oil filler cap off at idle. If crankcase gases pulse out of the valve cover in a regular, rhythmic stream, then you have a bad case of blow-by. That's caused in most cases by a broken compression ring. A leak down test is your best bet. You can also remove plug wires in sequence to see which cylinder is contributing the most gases to the crankcase. If the crankcase gets excessive pressure, it can come from one place - the combustion chamber.
B18 and B20 engines used different crankcase venting system - the B20 uses a system that is the reverse of the B18. Sounds like the previous owner was trying to deal with crankcase pressure. As George says, it doesn't matter which way the vent system flows - if there is excess gases, the problem lies elsewhere.

There's a bunch of wadded up wire mesh (the flame trap) in the top of the teardrop-shaped thingy (the oil trap). You'll see it if you pull the hose off, and you can pull it out with needle-nose pliers. It's one of those 50-cent parts that's supposed to be replaced every year and rarely is. If it's blocked with gunk, you'll build crankcase pressure.

However, I suspect you have problems beyond that. 20% leakage in two cyls might cause some pressure if it was leaking through the rings, but not heavy smoke. I suspect your head gasket is a goner and oil is leaking into the cyls directly.

In that case, your leakdown test by itself would be pressurizing the crankcase -- not sure if you'd be able to hear where the air is going or not... might well be time to pull the head and have a look.

I'm not sure it makes a lot of difference which hose goes where.
How do you know your oil pressure is high? Did you hook up a gauge?
or did you mean crankcase pressure?
How about oil changes? I'd change the oil and then cob it out
good and hard and see if it settles down any.

I am not familiar with your "pressure test" reading in percentages.
Is that a compression test? What actual pressures did you get?
Anywhere from 100 to 150 is common with higher pressures for "E"
engines and lower ones for worn rings and leaking valves. If a spoonful
of oil in each cylinder raises it, the problem is rings. Otherwise it
is probably valves.
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma