concept behind tuning

[Silverbullet]

so ya, i was under the influence of something ealier and i started thinking... Whats involved with tuning and why? Say you have stock injectors, turbo and MAFS and all you do is turn the boost pressure up, what are you changing when u tune this car? As you turn your boost pressure up, your boost guage will obviously read higher boost levels. Since boost guage reads off of fuel pressure, fuel pressure is increased as well so theres increased fuel to compensate for the increased psi. Whats the problem here?