Check the hoses coming from your turbo to the intercooler and from the intercooler to the throttle body. One may be split/cracked/leaking. If you get on the throttle it will blow air out.

This air has been metered by the AMM and the ECU will inject fuel for this amount of air.. But becuase some (or a lot) of the air has leaked away it will be injecting too much and it goes super-rich.

Relatively common problem on older turbo cars as the heat and oil vapours from the turbo slowly deteriorate the hoses from the inside out.

Bye, Arno.