spoke to a couple of mechanics about this and they have never heard of a cat causing this kind of problem, also the rattle was present one month ago and the car sailed through the mot no problem (same time), emisions were perfect gasses seem to escape ok from tail pipe and also there only seems to be one cat (part of the downpipe from manifold with lambda sensor on it) then to baffle and back box, I don't mean to sound ignorant but if i'm gonna spend money on a cat I would feel better if someone else had the same problem and resolve.
