It sounds as if it is running properly, but it is always possible that someone has altered the governor and it is running faster than it should. However your description of it dealing with tall grass with no problems sounds like typical PowerTorque - it is a big engine at 160 cc.
It could be a useful move to find another PowerTorque in your neighbourhood and verify that its speed sounds about the same as yours at full song. However if it responds smoothly to the speed control, and it starts and cuts like a dream, it seems you got a good $40 worth. Please don't forget to mix the fuel correctly, if you are used to 4 strokes. It won't last at all well on straight petrol.
