Embodiments of a compressor stage, in particular for a turbocharging system and/or a turbocompound, and a process for operating a compressor stage are provided herein. The compressor stage comprises an impeller, and a vaned diffuser arranged downstream of the impeller. The vaned diffuser is in fluid connection with an outlet of the impeller and comprises an injection device configured to inject a secondary fluid into the vaned diffuser. The injection device comprises a displaceable port at least partially arranged between an adjacent pair of vanes of the diffuser.