As long as the thing doesn't make any boo sound though, it's good enough for me!
The T4 is getting a de-cat as there only is one cat, that's it. On the BMW, it was plenty to get the two front cats removed and leave the center ones (probably high-flow ones in the eco-tune system). That way emissions also was no issue on NCT.
I NCT'd the car prior to selling it and it passed with the only comment from the tester, that he loved it and he had to take 4 attempts to get the handbrake to give enough braking power. Good thing there, because he liked the car, he didn't fail it on silly things.