Some possibilities, but like the foregoing posts, how are we supposed to know without seeing the car??
Dirty MAF screen => Inspect (do not touch); clean as required with CRC MAF cleaner. The ECU will alter throttle response to any dirt or fouling on the MAF
Too many short runs => take on 100-110km/h highway-freeway run with a tank of premium unleaded. Stop excessive around town/short runs as it builds up deposits
Dirty injector(s) (usually notified by a trouble code) => 2-3 tanks of premium unleaded + in first tank, add injector cleaner
Spark plugs => (requires inlet manifold removal) inspect for deposits and correct gapping. When was the last change?
Fuel filter => past serviceable
Fuel pump => sluggish performance sometimes a precursor to failure of fuel pump; as it progresses, engine can stutter, be hard to start, stall in reverse or on low fuel.
I am not in favour of disconnecting the battery to clear the ECU, which can make diagnostic interrogation by techies difficult with no data to fall back on. Do a "soft reset": place car in idle, handbrake on. Slowly rev the engine to 3,500 and hold steady for 10 seconds to reset ECU. Release then drive.
Bigdaddycool made a good suggestion to have the car seen by Holden for tech2 interrogation. Otherwise it's a lot of guesswork without actually seeing the car and sitting in it. Problems that require service are notified by trouble or error codes that can be interrogated from the cluster; tracing/interpretation is best left to Holden, not DIY.