It is sound more than anything really. I took one of the butterflys out and it is alot better!! Got a new unit on order at £300. Spoke to peugeot boys thismornig and they say that they are always going wrong but with different simptoms, a, because they rattle and b, because they stick shut. There is two flaps, one don,t open and the other rattles and sticks. Will inform you of the outcome tomorrow when the new bit turns up. Sam