  We present results of a semi-analytic model (SAM) that includes cold
accretion and a porosity-based prescription for star formation. We can recover
the puzzling observational results of low $V/\sigma$ seen in various massive
disk or disk-like galaxies, if we allow 18 % of the accretion energy from cold
flows to drive turbulence in gaseous disks at $z=2$. The increase of gas mass
through cold flows is by itself not sufficient to increase the star formation
rate sufficiently to recover the number density of $\dot{M}_*>120$ M$_{\odot}$
yr$^{-1}$ galaxies in our model. In addition, it is necessary to increase the
star formation efficiency. This can be achieved naturally in the porosity
model, where star formation efficiency scales $\propto \sigma$, which scales as
cloud velocity dispersion. As cold accretion is the main driver for gas
velocity dispersion in our model, star formation efficiency parallels cold
accretion rates, and allows fast conversion into stars. At $z\sim 2$, we find a
space density $~10^{-4}$ Mpc$^{-3}$ in star-forming galaxies with
$\dot{M}_*>120$ M$_{\odot}$ yr$^{-1}$, in better agreement than earlier
estimates form SAMs. However, the fundamental relation between $\dot{M}_*$ and
$M_*$ is still offset from the observed relation, indicating the need for
possibly more efficient star formation at high z perhaps associated with a role
for AGN triggering.
