Did another ride of about 80 miles today with the latest change, I removed the 1bbl to 2bbl adapter, and cut the mounting pattern for the Weber directly in the top of my intake plenum. I lost some of the big top end hit, but its much more ride able now. Im leaning towards it being lean (I still havent looked at the plugs, bad me!)
At about half throttle when the primary butterfly is fully open and the secondary is barely open there is a huge dead spot. If I feather the throttle to activate the accelerator pump, or go wide open it will pull through it ok but still feels down on power throughout the range. Also its very difficult to get rolling from a stop. I havent seen that there is any tuneability in the carb aside from the idle circuit so guess it time to start looking for jets.
Edit, also considering Picking up a VW type 4 manifold to try. My intake has a very large plenum with pretty crudely stuck in runners to the head. There isnt a very smooth airflow path there.