What did your manifold spacer look like? The one I salvaged with the 34DATA from the wrecker has a bigger area than the throttle ports on the carb, and I've been wondering if this 'step' between the carb and the manifold would cause turbulence going into the inlet manifold (air passing over that recess might be enough to create drag - and noise along the way). I'm going to take a shot at fabbing my own spacer in an attempt to eliminate anything that might interfere with air velocity into the manifold plenum...

Anyway the cause of your noise issue will make itself apparent. The novelty of having a Weber screaming at you will wear off pretty quickly and it will be something simple I bet.