[dangerousdferrari]

Thanks for your reply,

The noise can't really be described as a rattling which was being caused with the heatshield. That noise definitly went away when it was stripped, so I'm thinking that's not the problem.
Its hard to describe the noise but its a spluttery 'clicking' that only occurs unders acceleration. When crusing and when idle - even under some harsh revs, the exhaust sounds fine so it seems to only be apparent under the pressure of acceleration.
Further research seems to be pointing me towards the manifold(?) or as you do mention, the Cat.

Can anyone share anymore thoughts on that?

Thanks,