05 mazda 3 emission light
 

the emission light , light up about 6 mounth ago,i went to garage to fix it. the car was plug in, the probems seem to be catalyst and sensors wich that was replaced. it was fine for week, where i did put about 700 km on it the light light up again.back to the garage they plug it again show up exactly the same code same problem.they said cant be the cat. again. what woud it be then?

Did they replace the oxygen sensor? If it passes inspection it may be a false alarm.

it was done reset twice and the light still coming up after a few km the car passed trought the NCT but they reseted before it, now the rougle idle is up and down , car became a bit slower on take off then was before. the two sensors and the cat was replaced. thinking replace the spark plugs as well but thinking my self plugs has nothing to do with it. or does?