  Suppose that $G$ is a finite group and $k$ is a field of characteristic
$p>0$. A ghost map is a map in the stable category of finitely generated
$kG$-modules which induces the zero map in Tate cohomology in all degrees. In
an earlier paper we showed that the thick subcategory generated by the trivial
module has no nonzero ghost maps if and only if the Sylow $p$-subgroup of $G$
is cyclic of order 2 or 3. In this paper we introduce and study some variations
of ghosts maps. In particular, we consider the behavior of ghost maps under
restriction and induction functors. We find all groups satisfying a strong form
of Freyd's generating hypothesis and show that ghost can be detected on a
finite range of Tate cohomology. We also consider maps which mimic ghosts in
high degrees.
