This system is not converted. It had '134 from the factory. I've found that the recomended amount per the manual added to a fully evacuated system worked great in my '96 960. (I think is was around 2.2 lbs.)

This concept may be correct if you are replacing R12 with R134. I.E. if the original R12 amount was 2.2 lbs 2 lbs of R134 may be correct. The energy diagram for R134 is higher, so less probably matches the condenser/evaporator characteristics better for a system originally designed for R12.

Also, this system is controlled by the sensors, pump design, and ECU to be a "constant pressure" system. Therefore, the smart VOV never has a chance to show it's features and is of little value over a standard orfice. I'd doubt that an up-to-snuf system compared with either orfice would show any differences.

On converted systems they probably do a great job!
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'96 965 with 16' wheels at 103K. Had '85 745 Turbo Diesel for 200K.