I had all kinds of troubles getting my 2x Holley Webers to run on my Offy intake. It seemed like a vacuum issue but I couldn't find it. I finally traced the problem to the gasket between the carb and adaptor. The gasket just wasn't cut right and it was leaking in several places. I made a new gasket to fit and she runs like a top. As someone said, call Tom - he's the master on these carbs.
