Hi RBF. I cut the existing heater hoses outside the firewall, leaving appropriate lengths to allow fitting the valve.
I repurposed the vacuum switch for the manifold flappy valves, which I deactivated years ago.
Then I simply ran my own supply to the valve, with switch on the dash.
You can find a suitable vacuum switch on eBay. Saw one for BMW EGR that should be the ducks nuts.
Then you need a vacuum source, eg brake booster line or feed to VGT controller, etc.
Don't let the b'strds get you down!!