Resistivity measurements were carried out up to 8 GPa on single-crystal and polycrystalline samplesof CeCu2Si2 from differing sources in the homogeneity range. The anisotropic response to current directionand small uniaxial stresses was explored, taking advantage of the quasi-hydrostatic environmentof the Bridgman anvil cell. It was found that both the superconducting transition temperatureTc and the normal state properties are very sensitive to uniaxialstress, which leads to a shift of the valence instability pressurePv and a small butsignificant change in Tc for different orientations with respect to the tetragonalc-axis. The coexistence of superconductivity and residual resistivity close tothe Ioffe–Regel limit around 5 GPa provides a compelling argument for theexistence of a valence fluctuation mediated pairing interaction at high pressure inCeCu2Si2.