Yes and no. 650 AVS is a very good carb. Easy to tune and great aftermarket support. I've tuned mine to get around 17 mpg. Which is pretty damn good considering the fact that I have 3.55 rear ratio, 3 speed automatic (non-lockup) and an airgap manifold.
17 mpg at 70 mph at 3200 rpm's at 4500...