The missing check valve in the intake manifold would explain the leak at the throttle body and camshaft seals (positive crankcase pressure vents from the weakest point - often camshaft or crankshaft seals). All of these are somewhat common on th Cruze. The oil at the throttle body should go away if the Pcv System is functioning correctly
Edit: mixed up yours with another thread, sorry.
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Edit: mixed up yours with another thread, sorry.
Sent from my SM-G950U using Tapatalk