Hi Manu,
Since I reinstalled the game to keep up to date with the new version, I noticed that grunting is not available despite readjusting the NbType variable to 5 for both [Male_Grunt] and [Female_Grunt] in the tennis.ini file.
I've tried cutting the grunt variables (ie. Male and Female grunts and their variables) out of tennis.ini and pasting them into gamesys.ini and I've also tried including the grunt variables in both the tennis.ini and gamesys.ini. I've restarted the PC a few times as well -- all of which, reaped no success. This is guesswork, but there's probably some other 'variable' in a different field that needs a particular value to activate the grunting feature.... but in hindsight, I have no clue at this point what to do. If it helps (you may ask for this perhaps), here is the attached System.log.
Cheers.