I always tune for every modification, its just habit and good practice.

I have to re-tune the z06 in the next few weeks and its going to be a nightmare, new heads, lifters, rocker arms, pushrods, intake manifold, headers, throttle body and intake.

The tune I built for it before with the other parts is going to be basically useless.

Thats the way I was taught growing up and its just stuck with me.