No matter how well it passes the emissions test, removing either cat would technically result in a MOT failure because it is against the rules to remove or alter any factory-fit emissions equipment. Before you remark, "Well, mine passed without secondary," I'll respond: that's fine; we all know it happens sometimes, but it shouldn't. Both of my local test guys have been through mystery shop style inspections this year. One of them had a hollow DPF, which he found, and the other had an EGR that was missing (not programmed out). Now that he's doing so well on his tests, things will only become worse. Adblue deleters and kitten removers, take note: the Ministry will be pursuing you shortly, if not this year or even next.π