Hi again Jonathan,

My rule is for anything post 2001 you MUST use genuine parts, if the customer turns up with some crap he has bought off e-bay or the two makes I mentioned earlier send him on his way and do his own repair !

The number of times I have seen P0420 "cat efficiency" codes from garages fitting rubbish Chinese copy parts to post 2001 cars makes me laugh as,the car then has to go back in, another crap copy part is fitted and lo and behold it is back within a week and a half with the same fault code, a bit like your experience.

I hope you learn from this, your time is money you are losing.