In this work we have studied the maximal intensity behavior of the FWM signal with the changes in the molecular parameters Vo (corresponding to the electronic energy gap between the states involved in the model) and q (bond length alternation coordinate), from the valence-bond charge-transfer model. We have observed maximal values for the cases of extreme representation and minimal values at the intermediate representation. Moreover, for each value of Vo and q, there exist the respective optimum values of q and f, associated to the maximal values mentioned before.