Buy a Jett engine and you have a fast engine. No messing around with trying to tune the engine for more speed you just use it. You use a Jett tuned muffler with the engine and you don't have to tune it either.

Now if you want to "tune" your own engine, then you need to buy several of them. Then you carefully make the changes and log carefully the results of what each individual change does. when you make a change that makes it worse, you bin that engine. Then make all of the changes for the next engine but stop short of the change that made it worse. Then you would have a fast engine. You might want to make spares up too. usually the engines at max RPMs tend to wear out faster.