Adding a carb reduces the idle vacuum by about 29%
2^.5 = 1.414, 1 / 1.414 = .707, 1 - .707 = .29
Adding some initial spark (5 degrees?) may help, just crank it up a bit and evaluate results. The idle speed should go up; relax both idle speed screws the same amount to get the desired idle speed back. Vacuum should be higher. Throttle response may also be better. Road test, listen for pinging.
If it helps, remember to reduce the advance curve by the same amount as added to keep the total constant.
