Yaris with High CO Emissions & Code P0172

[rossh123]

Hi All,

My 1.0L 1999 Yaris had high CO emissions on the MOT report, it passed but was right on the limit. I also used Cataclean before that but obviously it didn't help very much. That was in March, and now a fault code has come up: P0172 System Too Rich. I tried using premium unleaded fuel for a few weeks but the code keeps coming back after I reset it.

Does anyone have any ideas as to what is causing these issues? I have attached the emissions report for more detail.

Thank You

[Mignon]

You have an air leak into the exhaust upstream of the cat.