Glad I saw you post this here as I think I might have put some noses out of joint if I posted on your thread on uk-mkivs

First of all, this does not mean that you are running lean at top end. That would flag up a system too lean DTC and the adaptation limit error would be (MUL) not (ADD). You'd also have early warning signs of backfiring and boost cutting before you get anywhere near engine melting temperatures. The ADD mixture adaptation refers to fuelling at
idle only which is why a vac leak is always the biggest suspect. I know you love searching for those
