Power fc question

[AngryRB]

Have been playing around in the last weeks with stuff like the intake cam gear and the tail section of the hks exhaust to see any difference in low down torque and sound of exhaust.

Each time i change anything it seems to make the power fc react, idle goes all wacky.  How does it know about such a small change such as that , eg 2degrees or a subtle change to exhaust?

Does it adjust itself or does it need retune for a small change?