Looks like i am on my own with this one

Decided to remove l/h cat to see if ok as they are common to melting /breaking up...all ok
Put emissions probe in manifold whilst off...excess oxy
removed timing covers l/h bank exhaust cam sprocket 1 tooth out!
Jumped due to heavy misfires caused by water ingress to coil pack...
Clue was misfires on all cylinders on l/h bank showing on autodiagnos.
lift it off idle to 1100 rpm all was well....valve train fault
simon