Here is somethink from the '93 transport manual: engine is mostly similar so this might give some useful indication, but not about the surroundings.....
www.avigex.ca/xport/ckpulley.jpg
or
www.avigex.ca/xport/ckpulley.pdf
I'd be most surprized that this pulley/balancer has degraded in a way it makes the car vibrate.....I'm almost sure the '88 3800 is of the "uneven firing" type and this creates a kind of vibration different from the "even firing" 3800 (L27) that I have and athat you have almost certainly in your '92.
However, it would be fun to have an "audio stream" of your vibration...we could build a sound catalog of noises on this forum...
just for fun listen to this one (starting my KIA)
www.geocities.com/lmp4203/Snd_2403.wav
(picked up with a digital camera)