Right, chamber-wise, it depends on the head & fuel quality/orientation.....the worse it is the less polish You'd want....if LM says it,....I believe it, because a lot of heads are fuel pattern challenged. The heat rejection of a mirrored finish just doesn't last, thermal barriers are the real solution, but I don't know what the long-term service life of those really are in critical areas i.e. street/dual purpose.