The dynamics induced by a seed pulse, resonant with the upper to intermediate levels transition, propagating in an ensemble of homogeneously broadened three-level atomic systems initially pumped by a two-photon excitation is analyzed in the presence of a very weak cw background field that is resonant with the intermediate to lower levels transition. Coherently and incoherently prepared systems are shown to have a distinct time-development. In particular, we show that, for the case of coherent pumping, the amplification of the radiation resonant with the upper transition is smaller for weak pumping, and is more delayed than that from a similar system which is incoherently prepared. For the emitted radiation resonant with the lower transition, we show substantial differences in the time-delay and generation threshold between the coherently and incoherently prepared systems.