I am trying to make the most of having more time at home, and probably looking too hard for projects that are best left alone, but...
I have noticed a "valve noise" coming from the passenger side of my 3.0 engine. It is more pronounced at start up, but never goes completely away. Not obnoxious and not noticeable when hood closed, but it is definitely very different from the drivers side. Using the long screwdriver method, the drivers side has a pleasant smooth sound, almost like a hum, lower in tone. The best sound I could compare the passenger side to would be like a sewing machine, and higher in tone than the drivers side.
I am definitely due to replace the supercharger coupling again. I will have it done, not going to do that myself. I have 120k on my car, and have always taken excellent care of it. Never had a real mechanical issue, just nuisance things. She still runs and looks great, and while in the shop I could do some other maintenance that isn't over the top.
So I thought I would solicit the forum for ideas of what would be the usual issues causing a similar noise, only from the one side.

 

High Pressure fuel pumps - they're on the passenger side of the engine.

Try the screwdriver method on the metal high-pressure fuel crossover pipe that runs across the engine and see if the "taps" are at the same frequency.