My previous car had sports cats that always struggled at mot time.

I stumbled on these things..



To my utter amazement they actually worked. The ‘logic’ being that sports cats flow too much gas and the downstream picks this up and throws and eml. The extender moves the sensor out of the flow and makes it less ‘sensitive’. Cheap as chips from amazon

https://amzn.eu/d/iiF5QzS