pappasmurf

Had my MOT yesterday on my fully decated Classic MY00.
The Co2 emissions test passed easily with the centre cat put back ( it wasn't far off passing without it ).
The problem was it was failing on what i think is the Lamda test?? forgive my technical ignorance but it's the test that shows as an upside down y on the test results sheet. It appeared there was an air leek somewhere.
After removing the itg filter and cleaning the housing case and pipes and putting it back in, it still failed...although better results. But when the ordinary standard paper filter was put in it passed easily.
My question is why? and what was wrong? At first we thourght the MAF sensor was no good.....but it seems to be fine.
Also, very importantly, there is no doubt the car is running much smoother now i have the standard filter in!?

can anyone help?

smurfy.

SiDHEaD

Should have got them to test the emissions from a different car. That's what I did (because mine failed even with the downpipe cat in place) saves the hassle.

Andy