That is a LOT of oil!
Idle air is drawn through the engine from the air filter and right side valve cover. I'd check to see that the hose on the right side (under the air filter and into the rear inside corner of the right valve cover) is OK.
More air is drawn in for the fast idle, so vac in the engine is higher while the auxillary air valve is open for fast idle. This would make the problem worse if the source air hose is plugged up.
The only other thing I could think of is oil standing in the left valve cover, and that isn't possible unless the entire engine is COMPLETELY full of oil....
You may simply have excessive blowby, but that would deposit oil in the air filter through the right valve cover at speed, and you would have gasses blowing out with the hose removed from the left valve cover.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!