I'll be happy to.
Changing to 134 causes the loss of about 20% of the a/c system efficiency. The MB's of the eighties had very little margin in the refrigeration capacity of the system. In our end of Texas it gets HOT and it gets HUMID. The a/c's in one of these marginal systems MUST be running at maximum efficiency if you wish to drive without sweating, thus 20% loss of efficiency is unacceptable.
This is not to mention that even a properly executed 134 conversion will up the chances of having a/c system problems at a later date.
Now, let me be clear. My statement concerns CONVERTING an original R12 system to R134a. Systems that were ORIGINALLY 134 were DESIGNED for 134. This meant many changes to provide long life as well as adequately sized condensors to make up for the loss of efficiency within a 134 system.
Most systems originally designed for 134 are just fine.
Have a great day,