Steve,
When I was getting mine installed, they said another option instead of integrating with the vacuum pump was to put a small compressor on one of the vacuum lines to simulate a lock or unlock. Another option was to install an actuator on the drivers door knob, which would mechanically push the knob up and pull it down. The compressor sounds like the best idea to me. Let me know if I can be of any more help.

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'95 E320 Sedan w/224K Miles (W124)