I have been hearing this god almightly rattle come from my standard exhaust and when I take it to Allan at Blitz custom exhaust (Hoppers Crossing, VIC) it goes away. when it does it, if i get a block of wood and push on the rattle from the cat goes away. Mind you its only done 66000 ks and failed already. For the record its never been hit or bashed, the mrs thrashes it i recon!!! So next week ive got it booked in for new high flow cat 100-200 cpi not sure which until the day and a straight through muffler. He did the high flow muffler on my 07 D4d hilux for $150 and made a big difference. turbo spooled up ealier and more torque. So ill keep you posted on the out come and total cost for cat, muffler and labour for guys interested in melbourne.