your o2 sensor fault will stay there, as even though you changed the cat it still don't work as well as the genuine cat, meaning the aftermarket cat don't meet the emission the factory cat did..

so you need to trick the 02 sensor or fit a factory genuine cat or get a flash tune to change the range of the 2nd o2 or have it switched off in the tune..

and from memory the turbo runs a 1.1mm plug gap and the n/a runs a 1.3mm gap. but running the n/a with 1.1 gap wont cause a problem...

now you know what owning a b series is about...
that's why I don't own one...