Same as Fig. 18, but confronting the predictions from Models 6, 8, and 9 (upper panels; dot-dashed, solid and dotted lines, respectively) and 10 and 11 (lower panels; short-dashed-long-dashed and solid lines, respectively). The different model predictions overlap. This suggests that the uncertainties associated with the treatment of mass loss and HBB in AGB do not have an impact on the predicted Y versus 10⁴ O/H behaviour.