Once you have run at least a full tank of petrol through the car take it back to Holden if it is still missing. Normally a miss is due to a faulty lead, plug or coil. Run over the leads and make sure they are all firmly connected.
Don't use that ethanol stuff - most especially the E85. One of the serious negative properties of that fuel is its excellent propensity to absorb water (moisture in the air/ water vapour/condensation in storage tanks etc.). Once it leaves the refinery it is absorbing moisture in the tankers, then when it sits in the tank in the service stations it is absorbing and when it finally gets into your vehicle's tank it is sitting there absorbing even more moisture. And you have about 65 litres of the stuff in your tank with a full load of 85% ethanol fuel. Eventually, with sufficient moisture, you get a condition known as phase separation where the water/alchohol mix separates from the fuel blend and sits in the lower section of your tank ready to be sucked up into your fuel system. When phase separation occurs you will have an upper layer of petrol with a milky layer of ethanol and water below it, and then in many cases a third layer of just water at the bottom. Phase separation will cause the engine to run very poorly once the injection system injests large doses of the contaminated product./
Ethanol is also an excellent and aggressive solvent . The ethanol will loosen up any dirt , scum, scale etc in the fuel tank and elsewhere in the fuel system and carry the fine debris to your nice clean injectors - that which gets past or does not pass through the fuel filter. Further, it will cause problems with rubber hoses, o-rings, seals, and gaskets. These problems are worse during extended storage when significant deterioration will take place. Hoses will delaminate, o-rings will soften and break down, and fuel system components made from certain types of plastics will either soften or become hard and brittle, eventually failing. Fuel system components made from brass, copper, and aluminum will oxidize to the point of failure.
The later commodores are supposedly E85 compatible but personally I would not chance it. In any event, even if the fuel system components are ethanol proofed from solvent deterioration you cannot prevent the scouring effect of the solvent delivering fine debris to your injectors.
I am not the least bit surprised your car is running better on premium petrol. The automotive industry is well aware of all the downsides of ethanol and Holden's advice to you about the contaminated ethanol (which is the water in the fuel) is most likely on the money.
I would never use any ethanol blend fuel. You just do not know how much water has already been absorbed into the ethanol once you fill your tank up at the service station pump.
