The issue I have seen is that it can burn out the o2 sensors bringing on the eml when the cats get overly hot. We saw this when we tried to get one through its emissions test on mot. near the end of the test the cats got hot, eml on, limp home mode. This had the same cat back system as yours too. Pretty sure it was the rev up engine (im new so only just found out about the different engines). But from what the owner was saying driving it daily never presents an issue. Also I don't know what standard of o2 sensors he had, if they were cheap after market ones, that could have been an issue.
It sounded lovely, quiet(ish) if you want it to be, noisey at about 2.5-3k revs. Didn't rev it higher than that though, no need and a customers car.
Jay