It sounds like it's running lean while it's cold. Try opening the GAV another 1/4 to 1/2 turn while the engine is still warming up. You can then try closing it a little once it's warm.
The 9N/2N/8N pipe is a lot smaller than a model A, even though they look similar in photos. I don't believe you'll get the flange to mate with the Model A exhaust manifold.