I guess this has been asked a 100 times already, but a bit gutted today as my pride and joy has just failed its first MOT under my ownership. It failed on emissions, fast idle CO2 0.63% 2 fast idle 0.46%,idle 0.43% tester says it’s the high flow cat failing. It’s a 54 plate Abbey tuned 350GT with 31K miles. I think the exhaust system is a fabricated one it’s been de-cat at some point with a central high flow sports cat fitted.
All other readings passed fine.
Do I change cat and if so who and what as not got a clue what to get ?
Do I put it through a Terraclean and see if this cleans the cat back up, although this will cost £100.00 alone with no guarantee it will work. Really do not want to change the whole system.
HELP !!