First check that all cylinders are firing.
With a fully warmed up engine do the following tests: Measure the idle advance with a timing light, with the vacuum hose disconnected. You should have around 7.5 degrees advance. Then connect the vacuum hose (engine running) and see what happens to the advance. It should stay the same (7.5). If it increases, then the throttle butterfly is not correctly adjusted on the carb, or the throttle positioning screw is resting on the fast idle position. Rotate the fast-idle cam so that the throttle butterfly closes all the way.
Every carb adjustment starts by setting the throttle butterfly closed position. This is critical so that the idle can be set later and so that the vacuum advance works correctly. To do the adjustment, the fast-idle cam must be at the "hot" position, where the chock plate is fully opened. Then unscrew the adjusting screw on the throttle lever, until it no longer contacts the fast-idle cam. In this position the butterfly is completely closed. Now you must tighten (turn in) again the screw until it just gets in contact with the fast-idle cam, and then tighten it 1/4 turn more. The butterfly must be just a bit open, so that it doesn't bind on the throttle body and wear it.
Now you can set the idle from the two screws on the left (as described many times in the past), and set the advance.
If this doesn't cure your problem, then swap the carbs. This would easily tell you if it's a carb tuning problem or not. The fact that both carbs have the same main jet (130) doesn't mean that they are jetted the same. You have to compare the idle jet, which is responsible for engine operation up to 2000 rpm. Also compare the emulsion tube/jet (the one under the carb cover, which looks like a tube with small holes on it's sides).
Check the float valve in the carb cover. It might be defective, allowing fuel to overflow in the carb and leak in the throttle bore.
Other reasons for excessive fuel consumption and poor low end performance would be valve train related: wrong valve adjustment, burned or bent valves. After adjusting the valves do a compression test (engine must be warmed up for a compression test).
Bill Spiliotopoulos, '67 Bug.