Right, I'll add that to my list then. Any links to what sort of pipe it is? I'm guessing similar to the one that goes into the right side of the air box, behind the filter, and into the rocker cover.
Could a poorly fitted air box also be a cause? I've noticed it wobbles around a bit, not the most secure feeling connection to the carb. I know it wont just fall off but it has a fair bit of play in it.