Well, after completing a successful evaporator and dryer replacement I vac'ed system out and refilled with 134. Ran colder than a witch's breast for about an hour then hisssssssssssss, lotsa vapor from under the hood, and you guessed it, blew out all the r134. Here's what happened and my suggested additional care during the repair:

1. Even thought I thought that I felt the garter springs snap on the nipples to the new evaporator at the fire wall, and I tugged on them to check, neither one was actually locked in. The only way I actually verified was to hold my dental mirror up to firewall and look to see the springs. I put a small screwdriver on the garter fitting collar, and gave gentle tap with a small hammer, and pop, the spring seated on both pipes.

2. When you loosen up the evaporator piping at the junction up behind the right headlight, be sure to not loosen, in any way, the other nut at the high pressure switch. I apparently made mistake of loosening both of them [they are identical] and could not successfully reseal the fitting w/o another trip to dealer for the fitting's o-ring.

Other than wasting two cans of 134, we are running cool now in 100d heat.
--
The Family Fleet '90 745 16v; '90 745 GLE; 96 855T; 99 XC approaching 900,000mi and going strong.