Thanks Jack. I suspect your first link explains his reluctance, as the ad said 'loud pipes'. But if people remove cats and such, how do they get them through the annual test? (Your equivalent of our MoT Test)

Anyway, machine now sold so that bubble has now burst.

Someone is than breaking a law very simple, right & with an altered defeat device, whether a person forges an instrument at testing facility, a physical device or software, it's all illegal here, unless with an exemption for conformity or testing and competition use I suppose?