The Kobrak-Rice extended STIRAP approach for selective population transfer has been tested for robustness vis a vis coupling to background states by examining preferential transfer to one or the other of nearly degenerate target states in the thiophosgene molecule. The calculations were carried out first within the original Kobrak-Rice five state scheme and then with inclusion of successively larger numbers of background states that have off-resonance radiative coupling with the original five states. Population transfers were calculated with and without use of the rotating wave approximation to determine if inclusion of the background states degraded the accuracy of that approximation. It is shown that the selective population transfer to a particular one of a pair of degenerate states is insensitive to the couplings with the background states and to the use of the rotating wave approximation.