Ive heard you all talk about the 4k rattle on numerous occasions, and I think its made me listen out too hard for it!
Mine is on 1k, and it sounds like a pig at idle (hot). If you tap the accelerator and let it rev and derev back to idle, the exhaust makes a rattley/tinney sound as the revs are building and dropping. Sort of sounds similar to when your cat is breaking up inside. Doesnt do it if you are driving normally, but only at idle.
Is this the "4k" rattle or yet another problem I can add to the list when I throw it at Renault to look at. It certainly didnt make this noise when I got it - sounded more whistley and modern at first. Im just confused!