3 and 5 amp alternators seem to be the most common. Above that output they seem to have voltage regulators mounted separately on the engine.
I'm only aware of Briggs having California emissions versions, and everywhere-else versions, of their emissions control systems. Even there, they are migrating toward selling the California version everywhere, so I think it unlikely the Australian version would be different from the UK version. The "usual" unleaded fuel in most countries is 91 Research Octane Number, with 95 and 97 or 98 RON available as premium products. However in the past ten years or so most of Europe, including the UK, has made 95 RON its standard-grade fuel. Hence your regular grade UK fuel is higher octane than our regular grade Australian fuel. If your engine is misbehaving I doubt it is directly a fuel problem. It may be carburetion, or an air leak, or a malfunction in an "anti-afterfire" solenoid, or various other things. Are you sure you don't have some water in the carburetor float bowl or the fuel tank?
Your Intek engine is prone to malfunctions that can cause problems related to what you are experiencing. In particular, they blow cylinder head gaskets, and wear out their crankcase-pulse-operated fuel pumps.
