Actually, you have that backwards. AAS gains will happen over the entire muscle system (well, the ones you exercise), whereas IGF (if injected IM) gains will be mostly specific to the muscles injected. That is why strength gains with IGF are hard to quantify. IGF can affect many things, but injecting IM will concentrate its effects in the muscles injected. It is the only substance that has a site specific effect. Now if you inject IGF subq, it will affect the body overall much more and may include organ growth (at really high dosages).