  We present the bulk thermodynamic properties and phase diagram of strongly
interacting matter in an extension of the 3-flavor NJL and PNJL models of QCD.
Using a three momentum cut-off scheme, we have extended the multiquark
interaction terms up to eight order so that the stability of the vacuum is
ensured in these models. We explore the effects of various combinations of the
two eight-quark couplings $g_1$ and $g_2$ and present a comparative study
between the NJL and PNJL models as well as Lattice QCD data. The main effect of
the eight-quark interaction term is to shift the critical end point in the
$T-\mu$ phase diagram to a lower value of $\mu$ and higher value of $T$, thus
bringing them closer to Lattice QCD results.
