[alfadoc]

I have zero experience tuning Webers on a Porsche, and decades of experience tuning Webers on Italian cars. I believe a lot of your problem is synchronization. With IDFs and DCNFs there is a plug that can be removed at the base of the carb, near the idle air correctors and the idle mixture screws. These passages are connected to the venturis, and to the air flow at idle. I have little brass tubes that I have threaded to fit into these plugged holes. Then I use a multi column vacuum manometer to measure flow, as is used in motorcycle shops. I disconnect all linkage, close the idle air correctors all the way, then match the highest flowing barrel to the lower flowing ones by manipulating the individual carb idle adjustments. Then you balance the barrels in the carbs with the bleeds. Works a treat on a V12 Ferrari. Probably harder to explain than to do. Hope this helps.