actuator tests mean they can check the sensors and coil / injectors whilst the engine is running - get voltage read outs
for example they can test the current draw from injectors whilst they are running, they can turn off injectors individually
they can basically turn every sensor off individually whilst the engine is running
check relays and solenoids and actuators
it sounds like your car needs to be hooked up and taken for a cruise by a vxhall mechanic and then make a judgement based on the data feedback
usually vxhall mechanics just keep replacing each part until they found the problem, for example customers are not allowed to return electrical parts but if you look on the parts computer you will see mechanics taking stuff out of the parts department and returning em when the fault is still present
coil packs for example, my m8 who works for lookers parts department says he had only sold 4 coil packs in a year over the counter but he said the mechanics their borrowed coil packs 16x times or sommit meaning coil pack is never usually the problem