  We investigate dispersion and absorption properties of a weak probe field in
a four level atomic system through interacting dark resonances. We show that
two narrow peaks appears in the optical spectra due to the presence of
interacting dark resonances. This two narrow peaks leads to the superluminal
light propagation with strong absorption. However, if a weak incoherent pump
field is exerted to the probe transition, then the peaks structures can be
changed such that two absorption peaks transformed to two gain deeps. We Show
that both subluminal and superluminal light propagation occur in this system,
where controlled by the incoherent pumping strength.
