Every time I give people running lessons, I keep insisting on the fact that they need to learn how to breathe correctly in order to run properly. Running like any other sport require a big oxygen supply in order for the muscles to maintain their performance. My advice to you is to get as much air as possible using both your nose and mouth to inhale. Making use of your diaphragm instead of your chest will give you an extra space to store oxygen so your muscles get enough of it.
I know that everyone can recognize professional posture when they see it. Your arms, shoulders and legs position can increase your running performance easily. The thing you should keep in mind is that you need to stay steady and consistent during your running session. If you don’t do that, then you might end up injuring yourself. If you lean your body forward, then you are going to make use of gravity to increase your running speed.
I’m sure that you don’t want to put all the running stress on only one leg. In order for you to keep your balance, you need to distribute every action equally on the body muscles. While leaning forward could help you increase your speed, it could also affect your balance if you don’t do it properly.