It could still be a leak, you should drop the belly pan and see if it's filled with oil.

There is an oil/air separator built into the valve cover on 60x engines. It's workings are sort of a mystery, as the assembly is riveted together. It includes a pressure activated valve, a drainage chamber and a drain that allows oil back into the head. It's possible that either the valve is stuck, allowing blow by pressure to blow out a main seal, or it could be that the drain is clogged, allowing recovered oil to be sucked into the turbo. There's a tiny hole on the side of the valve cover that allows air pressure to equalize in the valve, if it's clogged the valve will stick. If you can't find any other possible cause, it may be worthwhile to remove the valve cover and clean this assembly out as best you can.

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