I suppose it wouldn't be a bad idea to put some new valve cover gaskets on and take a peek, but I won't have access to my dad's shop until this weekend so it will have to at least wait till then.

In the meantime, I noticed that the noise is present and identical when the motor is totally cold and hot. Maybe the tensioner has totally given out?

If I hover the TPS at around 750 rpm, I can hear the sound change to a more steady version (but definitely there) that is more or less hidden by the increased regular motor noise.

If it's the timing chain, my guess is that it's a light graze on the top driver's side guard