I will look into the Walker cat, thanks.
I don't want to have to change the gaskets if I don't have to, but I don't want to ruin another cat either. So a sensor failure can bung up the cat in say 6000kms which is about how long the CEL has been on and going heavy on gas?
I might have topped up the coolant with some green stuff a while ago which made the sludge I had to flush. I put Dex back in it. Now I read Dex isn't that good an idea either?
Thanks for the advice 'Scottydogs'