If anyone thinks Usain Bolt ran 9.58 simply because of EPO is blind. The guy is the fastest human ever - physiologically. Same thing with El Guerrouj. What drugs cannot do is make perfect biomechanics. Once you understand this, you will understand athletics.
You're a hobby jogger like most of us here aren't you?
Of course drugs can help perfect biomechanics. Drugs can make you train for longer and more often at your target pace. Doing that would improve your biomechanics in a race. Even I know that.