There are 5 ways for that oil to get there;
1) through the carb
2) between the carb and the ports
3) the ports
4) the guides
5) it is coming back up from the chambers
1) the oil is in the gasoline,or it is the PCV system operating in reverse,at WOT, through a connector pipe, like the factory runs;the proof being an oil-soaked air-filter
2) is the PCV system operating in forward mode,pulling excessive oil from the valve cover. An alternate source might be a faulty brake-booster, but that would then be brake-fluid.
3) is the gaskets.Or more often,machining errors. The angles can be bang on, but if the two flanges are trapezoidal; narrower on one end,you got trouble.
4) well, it could be through or around them, and a late closing intake could blow it back up the port.
5) most likely rings. But for this level of oil to be coming from faulty oil-rings, there would also be plume of oil-smoke out the pipes, and the low LD results,kinda negate this.So I wouldn't be worrying about oil-rings just yet.
1 and 2 are easy checks.4 is hardly likely. and 5 is extremely unlikely.
So that leaves 3 as the most likely
