When you hooked up the pressure gauge, what was the pressure in the system?
This is info from my 93 manual;
The code 23 is "Pressure Switch Circuit"
Open in pressure sensor circuit
Abnormal refridgerant pressure
(below 28 psi or above 455psi)
Harness or connector between pressure switch and A/C control assembly
Refridgerant pipe line
A/C control assembly
If you need it, the pressure switch is located behind the passenger headlight.
The vibration; The driveshaft (actually called Propeller shaft) does have a support bearing which wears out. Mine is shot and I feel the vibration in the seat and on the floor at my feet. I know the propeller shaft needs to be balanced and there are different weights to put on it. Here's a link to the parts of the propeller shaft. Hope it helps ya out. http://lexus.sewellparts.com/oem-cat...S400-1994.html