I work for Holden, so I'll try to help you here.
With 200 thousand kms on the clock, it could have one or more of many reasons why your car is not right.
Could be carboned valves not seating, other coil (especially if non-genuine), weak failing fuel pump, wiring fault at fuel pump, faulty ECM, fuel injectors blocking up, stretched timing chains, cam phaser issues from poor service history etc.
So, to me, I can see you spending some money, could be $300, could be $3000.
I would certainly get it looked at asap.
I see it a lot these days, where the owner doesn't think it will be much, and like this week, we quoted 3 engines.
Hope this is some guidance for you.