Give the car a good service first up, engine oil and oil filter, fuel filter , also replace the air filter whilst your at it. Sparkplugs, plug leads and the 3 ignition coils should also be replaced if theyre more than a couple of years old or so ,
(go with genuine holden coils if you replace them, most cheap aftermarket coils are usually rubbish and give false economy).
These EFI engines run very high voltages in their ignition systems, and this wears out the plug leads fairly quickly. I replace my plug leads every 12 months or so to keep the car running at its absolute best..After 12 months or so, most plug leads will be just starting to get onto on their downhill run. Ive seen faulty leads or coils cause hesitations or misfiring etc whenever the engine is put under any sort of load, but the engine will seem to run fine when its just sitting there being revved in neutral ..Also run a couple of tanks of 98 octane fuel such as BP ultimate or shell Vpower along with a bottle of injector cleaner to give the fuel system and injectors a good cleanout. (it will also help to do a few full throttle starts up to the speed limit whilst the injector cleaner is in there).
I noticed that your cars an auto, and you can also service the auto trans yourself and save a fortune, theres no band adjustments to make etc, just remove the trans pan, remove the old filter, fit the new filter, refit the pan and fill the trans with new fluid. 5 litres of dexron111(3) type auto trans fluid is around $30 to $40 and a trans service kit , which comes with new filter and pan gasket, cost around $25. These cars run way better when the autos are kept serviced regularly.
