  We compare simulations, including the Illustris simulations, to observations
of CIV and CII absorption at z=2-4. These are the CIV column density
distribution function in the column density range $10^{12} - 10^{15}$
cm$^{-2}$, the CIV equivalent width distribution at 0.1 - 2 \AA, and the
covering fractions and equivalent widths of CIV 1548 and CII 1337 around DLAs.
In the context of the feedback models we investigate, all CIV observations
favour the use of more energetic wind models, which are better able to enrich
the gas surrounding halos. We propose two ways to achieve this; an increased
wind velocity and an increase in wind thermal energy. However, even our most
energetic wind models do not produce enough absorbers with CIV equivalent width
> 0.6 \AA, which in our simulations are associated with the most massive
haloes. All simulations are in reasonable agreement with the CII covering
fraction and equivalent widths around Damped Lyman-$\alpha$ absorbers, although
there is a moderate deficit in one bin 10 - 100 kpc from the DLA. Finally, we
show that the CIV in our simulations is predominantly photoionized.
