I will stay away from the brake booster line.
The carcoal canister comes off a small elbow at the top of the plenum and I'm not using the PS at all, I have removed it and capped off the pipe that runs to it so I will see what I can rig up using that.
And thanks to you as well Norbie, it was the location of the S/C that was throwing me when it came to finding a good pick up point for this gauge.
Cheers,
Mitch.