We have a standard practise to remove the top cowling and make a full visual check at least daily too.
We check the engine mounts, all hoses, plug caps, electrical connections and safety-wires.
In France we don't have the L1, L2, L3 qualifications, every pilot is 100% responsible for his or her machine which is why we don't trust anyone else to have done anything, we check ourselves.
I don't know the Jabiru engine, so I didn't know that the intake manifold is not visible from above.
Sounds like those bolts should be safety-wired.