This just in!
Tomorrow I plan to add the most expensive, rarest, most effective "Go Fast" part to my bike that it's possible to add.
ME
Gonna get on it and go ride. Take the $140 part you're going to add and instead put $140 worth of gas through your bike and I guarantee my friend, you'll go a lot faster than if you put the part on it.
Wanna trim some weight off that bike? Carbon Fiber levers, magnesium foot pegs, titanium bolts? Eat one less Philly Cheesesteak per week and not only will you not have to pay for the hard parts, get the benefit, and go faster, but you'll live longer too.
Professional racers may be able to go "psychotically fast" even when bloated and pudgy, but as mere mortals, the easiest and most effective way to gain skill on a dirt bike is to get your body in shape. You'll ride longer, harder, crash less, resist injury easier, and because of all this, gain skills faster.
Remember the absolute best part of your bike, is you.