I put a slightly used Weber carb kit on (don't know the history of it, bought online, but it's very clean and almost new looking), hooked everything up (including the water line, thanks Phil!), adjusted the choke (manual), idle and idle mixture and the car idles beautiful. I get in the car, stomp on the gas and the engine falls flat on it's face, gasping like it's starving for fuel and going nowhere. If I give it some choke it runs better and is drivable. It was 50 degrees outside while this happened and I drove the car for about 30 minutes to make sure it was completely warmed up, no change.

The idle mixture screw ended up at about 1 1/2 turns out so the idle jet is perfect for this motor (a stock B18). It seems like it's running too lean though, because there is no smell at all to the exhuast (and no black smoke or anything when stepping on it). The engine was tuned up prior to replacing the carb and with the old SU's it ran fine without choke (however the old SU's were running rich). I changed the spark plugs today, but it made no difference. I'm assuming it's a float or main jet problem with the carb. Disconnecting the vaccuum advance didn't seem to make any difference either way. Any ideas?

Here's a picture of it: