This site is amazing!! Thank you to all who offered up suggestions - and I wanted to update you on the diagnosis.

Finally put the car up on the lift this weekend. The u-joint was worn - but was not an obvious source of the issue. After getting the vehicle up to 25 mph you could see the shaft begin to flop near the center bearing. Upon closer inspection it became clear that there was a small rip in the rubber boot on the center bearing support.

I'm not sure, like the chicken and the egg, if the tear in the boot is causing the wear on the u-joint, or if the u-joint caused the tear in the boot. Regardless, I am now a member of the front wheel drive club and will spend the summer deciding if I should rebuild the shaft using the FCP Groton kit, or perhaps will just order a remanufactured shaft.

For anyone seeking to remove their shaft you will need a 12mm socket to remove the center bearing support, and a 6mm allen wrench to remove the bolts at either end of the shaft. Removing the enter center bearing/exhaust support plate makes things go a lot smoother. As does having an impact gun for the allen bolts so you can keep the car in neutral to rotate the shaft.

Thanks again.