[vettestr]

We use the Power Master brake unit from Buick Grand Nationals but many Buick models used it as well. Our choice to use it was driven by ability to keep the firewall clean and uncluttered as all our units are remote mounted. Another reason and plus is the 4 wheel 4 disc brakes need a larger volume of fluid movement than a mechanical system can support. We do use an adjustable proportioning valve to balence the system. The system when adjusted properly gives you a perfect solution with low pedal effort yet great feedback to the driver and is a very linear assisted pedal.
The unit took some hits for a bad reputation in its day but was more electrical support problems on the Buick side. One problem with unit its self was solved with a grey switch that replaced a problematic black control switch. Make sure you have the grey colored switch.
The vac motors to supplement a low vac supply still need the firewall mounted unit so you loose the cleaner look of standard Tilton master cylinders but they do work.