don't shut off the idle fuel supply to the front carb. you idle off all 4 primary bores and you don't have factory smog carbs. if your using an electric choke on the back carb, similar to factory; then the mixture screw next to the choke will want to be about one turn further out than the other three due to extra air flow being pulled thru the choke. idle jets should be around .033"-.036" for good idle quality. step up springs may need a changed from the oranges to something lighter with that cam. somewhere around 1 1/2 turns out on the three non-choke bores and about 2 1/2 turns out for the choke with proper idle jet size should work well.