My car is the ly7 but having the same issues. Due to my car running a haltech ecu I have narrowed down the issue to several things possibly. Throttle body not opening on startup, too much fuel being sent to injectors on startup. Timing on startup.
The reason why I know it's something to do with this is due to my car being heavily modified and when playing with the haltech and to stop a stalling issue I opened the throttle body 1% at all times when running. As soon as I did this the noise just after startup stopped.
See if Holden can see any faults within the ecu itself it may be faulty or the electronic throttle body actuator or system could be the issue.