I've had 2 Janspeed sports CAT's, the first broke up after a year and the 2nd replacement CAT under warranty triggered the EML light and failed the MOT emissions test.

I never had it up on the rolling road but I felt that there was an increase in power.

Now have a shity standard CAT from online automotive that is triggering the EML light anyway! Getting it changed back to original ford CAT I think.