That green Victa vantage you have there I believe is only available at Bunnings. The new ones are blue instead of green. I do not believe Victa dealers sell them. That is the model with the single bar blade instead of the normal 18" victa blades. A common problem with those is that they surge at full throttle. This is due not to carby related problems, but happens when the bar blade wears over time. When the blade wears it doesn't provide enough weight to the crankshaft and thus becomes much lighter than when new. The way to fix the surge is to replace the bar blade.
Just a tip for you Blumbly as many come in at work.