On my bike, with a delkevic exhaust, I had to use bigger idle jets to get rid of the low throttle stumble. I know some others, at least with US models, had to go bigger on the idle jets. From memory, I want to say I went up two sizes from 37.5 to 42.5. I am pretty sure I posted in this thread somewhere. I think once you get past about three turns, you aren't doing much and need to jet up. I will say, once it was dialed in, it ran awesome.