MOT air/fuel ratio

[foRSter.]

Been that time for me today, I'm lucky enough to have a friendly MOT'er who didnt require me to put my cat ect back on. He said to me that he tested the emissions anyway to see what it was running like. When in idle he said its not too far off passing, but gently taking the rev's to 1500-2000rmp it run's really rich, 10% on air/fuel ratio and that his 500bhp cosworth wouldnt run that. I'm no expert on this and the car is booked in for some tweeking soon, but could this have any negative effect on the car in the mean time? Should I take it easy until the tweek?

 

[RSTuning]

That's rich yes, need to look at that sooner rather than later tbh mate, ring me Monday and we'll have a look at it

 

[foRSter.]

Will do, Could this cause excessive fuel use?

 

[RSTuning]

Yes of course, which is pretty odd as i always get it as close to lambda a possible then use the sensor for any correction. We'll see what's wrong no problem though