Identical two-particle interferometry provides a scenario where interference and exchange effects manifest at once. We present a detailed calculation of the detection patterns in the two-particle two-slit experiment by extending Feynman’s Gaussian slit approach to multi-mode states. We show the existence of two regimes depending on the mode distributions. In one of them we find a novel behavior for bosons, with detection patterns almost equal to those of distinguishable particles although the overlapping is large. As a byproduct of our analysis we conclude that the interaction at the diffraction grating is an efficient method to increase the initial overlapping. We propose a scheme, within the reach of present day technology, to experimentally verify our results.