with the balance, screwing it in too far will open the left carby too far, screwing it out too far will open the right one too far.
make sure the idle stop is touching on both side, adjust the balance to make sure. If u ahve a vacumme gauge u should be able to use this.
with the mixture, if they arent factory items chances are the jets have been change and so on. so screw the miture out about 2 turns then turn it about quarter turn and wait 5 seconds or so. try and find the highest atainable idle,
so start with number 1, find its highest idle with the mixture, once done lower the idle and go to number 2, get the highest idle then knock the idle down. so on for the rest.