Lots of beginners ask the same question, "how can I get more power", about engines.

First thing to do is try a couple of different props. More times than not, beginners bolt on the prop somebody said was the best for the engine and done nothing since. Seldom is somebody else's opinion better than the opinion of the engine on your airplane. And more times than not, you'll find better performance if you test a few props.

As for boosting the power of most engines, beginners won't come close to being able to do anything of the sort. Higher nitro is about it, unless there is a muffler made for the purpose. There used to be a "tuned pipe" muffler for that size engines. It wasn't actually a tuned pipe but it looked sorta like one and it actually did up the power a bit.

Simply running the engine with a prop that'll let it turn higher rpm gets more horsepower, but unless the engine/airplane combo like the new pitch you won't gain a thing other than louder noise.