If they're original equipment Nitti, why not try to get the MOT with them in place unmodified? They might not be THAT loud, and I'm not sure what the UK decibel limit is these days. You aren't going to be running it at full blast under load at the MOT station are you? Holding wire wool and brillo pads in, and other stuff, isn't trivial. They also collect moisture which means rust from within, and they may provide more back-pressure than the carburettor is tuned for on the open road. Sympathetic testers surely exist over there, who appreciate seeing and hearing something that looks and sounds how it was made? They must exist, as many of my UK mates run things that are pretty rorty. I don't know, as I haven't been for one of those meaningless UK MOTs for years and years, but I am sure that original equipment on original machinery can and should be OK. If it were me, which it isn't, and if there were a prob with the MOT, I'd shove anything on to get it passed and then revert to what it should have. Yes, the police get all excited about Japayamakawas running around at 12,000 rpm with after-market illegal exhausts in the countryside, but they'll leave you alone on an A10, almost for certain. I'd just go for it, subject to better advice from UK residents who've fallen foul . . . Groily