  We derive an expression for the drag rate (i.e., interlayer momentum transfer
rate) for carriers in two coupled two-dimensional gases to lowest nonvanishing
order in the screened interlayer electron--electron interaction, valid for {\sl
arbitrary} intralayer scattering mechanisms, using the Boltzmann transport
equation. We calculate the drag rate for experimentally relevant parameters,
and show that for moderately high temperatures ($T\gtrsim 0.2 T_F$, where $T_F$
is the Fermi temperature) the dynamical screening of the interlayer results in
a large enhancement of the drag rate due to the presence of coupled plasmon
modes. This plasmon enhancement causes the scaled drag rate to have a peak (i)
as a function of temperature at $T \approx 0.5 T_F$, and (ii) as a function of
the ratio of densities of the carriers in the two layers when their Fermi
velocities are equal. We also show that the drag rate can be significantly
affected by the {\sl intralayer} scattering mechanisms; in particular, the drag
rate changes approximately by a factor of 2 when the dopant layer modulation
doped structures are moved in from 400~\AA to 100~\AA.
