Via chi¿¿(Q,E) we aim to investigate the dependence of the Kondo temperature TK of YbInCu4 on external pressure and substitution. YbInCu4 undergoes a first-order isostructural valence transition as function of temperature, very much like the pressure driven gamma -> alpha transition in cerium metal. It is generally believed that the phase transition is driven by the pressure dependence of the 4f conduction electron interaction which causes the Kondo temperature to be very sensitive to pressure. The pressure dependence of the Kondo temperature is therefore an important input parameter for modelling the phase transition. Substitution with Y has the same effect as external pressure, most likely due to chemical pressure on the Yb lattice site. Comparing data of YbInCu4 under pressure and of Yb1-xYxInCu4 will yield insight whether doping causes effects due to disorder.