hi guys.
recently my engine management light has been coming on showing a fault code relating to the lambda sensor/ cat. however, i do not have a cat as i fitted a full zorst system a couple of years ago. shortly after doing so i sold the car to my mate. i then bought the car back off him about 6 months later and the light never came on. ive been driving around now for about 2 years and its come on??? ive looked at the lambda sensor for anything obvious and cant see anything. when i phoned my mate and asked him where and how he fitted the MIL eliminator he couldnt remember if he did or not??? i thought he did but now were not sure. so, question is, what does the MIL eliminator look like and where would i find it? also, if one isnt fitted, is it possible to drive around for 2 and a half years without the management light coming on and then all of a sudden it comes on?

any help appreciated.

(appologies, also posted this in general discussion.)