If you are just learning to fly then you don't need to worry about being robbed of power. The engine on that plane is fine just the way it comes. I can't think of any manuever that the Superstar is capable of that that particular engine/muffler combo won't power it through just fine. If you're anything like me when I learned to fly, you will be wanting to slow that plane down at first.
Later on when you become comfortable flying you might want to look into putting a ball bearing .46 on that plane or your "second" plane. You will be fine for now though.
Michael