Yes absolutely, too high a CR means you have to retard the timing so much you end up gaining nothing from more boost.

HOWEVER, the higher your RPM gets, the higher the "workable" CR at any given boost value is.


So its a triangle really, of boost vs rpm vs CR

And there is a different triangle for each fuel you use, if you are on 102ron then 9:1 is nothing even at big boost at moderate RPM