You're spot on with that, Mark. Even on a short run today it sounded better and less boomy to me. I think I may just learn to love it.
However, the misery isn't quite over. Opened the passenger door to Kat's Micra to find the Nismo had been rubbing the cheap, crappy plastic on the door card and has left a load of nasty scratches. Apparently, I have to grovel.......