  The promising thermoelectric material TiS$_2$ can be easily chemically doped
and intercalated. We present here studies of single crystals that are
intercalated with excess Ti or Co, or substituted with Ta. We demonstrate the
intrinsic impact of these dopants on the thermal transport in the absence of
grain boundary scattering. We show that Ta doping has the greatest impact on
the thermal scattering rate per ion added, leading to a five-fold reduction in
the lattice thermal conductivity as compared to stoichiometric single crystals.
