Downunder, it's probably not your plug causing this. The only real benefit you get from changing plugs, is on the bottom end. If it's clearing out when you punch it, it's fine. If it bogs on the bottom, try a hotter plug. What engine is it?
Usually stalling problems are either the tune, the clutch, or the engine condition itself. Is there good compression, or "pinch"? Is it new? What engine are you running?