the ports you hook your Carbmate to in order to sync at idle are the same ones to connect together with a vacuum tube afterward.
if you don't use the old egr ports that David suggests make sure they are capped off properly with thread sealer so they don't leak air.
Advanced Carbmate technique: buy 2 8' or so sections of vacuum tube the same size as supplied with the device and wire in a cigar lighter plug instead of or with the battery clamps so you can have it in the cabin with you as you drive. I put the tubes through the small triangle pasenger vent window and leave the Carbmate on the seat. That way you can hook it to both ported and manifold vacuum ports and see how the carbs behave under real driving conditions and adjust accordingly, usually a compromise between idle and 3000 rpm or whichever your engine responds to better. This will tell you if your linkage is whack. I always use mine hooked up this way and just look at the unit through the windshield when synching at idle.
if you don't use the old egr ports that David suggests make sure they are capped off properly with thread sealer so they don't leak air.
Advanced Carbmate technique: buy 2 8' or so sections of vacuum tube the same size as supplied with the device and wire in a cigar lighter plug instead of or with the battery clamps so you can have it in the cabin with you as you drive. I put the tubes through the small triangle pasenger vent window and leave the Carbmate on the seat. That way you can hook it to both ported and manifold vacuum ports and see how the carbs behave under real driving conditions and adjust accordingly, usually a compromise between idle and 3000 rpm or whichever your engine responds to better. This will tell you if your linkage is whack. I always use mine hooked up this way and just look at the unit through the windshield when synching at idle.