When I bought my Amazon it stumbled on acceleration and I wrestled with my Weber (came on the B20 in my Amazon when I bought it) for quite a while trying to get it right, and when it came time for a new exhaust system I had a port welded in so I could put a wide-band A/F meter in. Before you start drilling out jets, try going in the other direction. Now it is possible that there is something screwed up internally in my Weber (tough I've rebuilt it, new diaphram, o-rings, etc. etc.), but I have the absolute smallest primary idle jet available (I think) in mine and it still idles a little bit rich, but otherwise runs very well. I spent a lot of time fiddling with the carb and watching the numbers on the A/F meter trying to get things smooth and with good economy (last I calculated it I was getting around 29mpg, and had good power). Of course every engine is a little different, particularly with the various mods, exhausts systems, etc. one can put on, but here is what I currently have in my DGV according to my notes:
main idle 40, sec. idle 42, main 150, sec. 140, main air cor. 165, sec air cor. 180.
Per the A/F its STILL a little bit rich at idle and it gets a tad lean at highway speeds on a long, slow incline.