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The properties of the circumgalactic medium (CGM) are governed by the details of galaxy formation comma evolution and feedback. The high ionization lines of OVI are the most effective probes of the warm-hot CGM of L* galaxies comma because the ionization fraction of OVI peaks at the virial temperature of these galaxies. An important observational result in this field was published in Science it showed that the prevalence and strength of the OVI lines depend on the specific star-formation rate (sSFR) of galaxies. However comma there is a clear correlation between sSFR and stellar mass in the observed sample comma so the governing parameter may be mass instead. Theoretical simulations are also providing conflicting results comma therefore new observations are needed to inform the theory. We propose to probe the CGM of L* galaxies at a range of sSFR comma but at fixed mass. We will thus determine whether mass or sSFR is the driving factor of CGM properties comma or there is additional physics. This will be a major step forward in our understanding of the physics of gas inflows and outflows comma star-formation and feedback comma and their relation to halo mass. This small program will greatly enhance the scientific return on previous investments of hundreds of orbits by clearly distinguishing between the possible scenarios.