On the bottle of cataclean there are instructions for the use of it, do it tomorrow and have some fun whilst out to get the cat upto temperature and allow the cataclean to do it's work. Had my MOT a couple of weeks ago, I normally run a GEMS ECU so fitted the OE ECU and took the car for a good run. I had chosen a MOT station 20+ miles away so the car was nice and warmed up. He did the fast idle test then the idle test car passed so I was happy. Hope you get it sorted. Steve