I generally agree with the above posts - to a limit. The normal idle jets for these carbs on a 2L Alfa engine are 50F8. I like to run a little lean and I prefer 50F11. But if he has these jets and he still has the problem and it is alleviated by screwing out the idle jets, then I say he has either an air leak or low float level. I don't agree that putting in bigger idle jets is the solution. It may mask the symptoms but not cure the problem. Say he has an air leak and he makes his engine run better by installing 55F8's. Then the leak gets bigger. What should he then do, install 55F9's?