An odd and depressing noise

Ah, the latest in the farcical Corvette saga. A mysterious noise has appeared!

Initial diagnostics suggest it's coming from the valvetrain on the passenger's side, but a cursory inspection didn't turn up anything obvious. Based on careful listening with a rubber hose stuck to my ear, I'm guessing it's the exhaust rocker, pushrod, or lifter on the #4 cylinder. I'll dig into it this weekend.