Somewhat of an annoying day! First MOT after 3 yrs of trouble free motoring.

Fitted a CAT, with the current map in the power commander was getting ~1.2%CO, ~400-600HC.

Leaned the map out down to -5 ~ - 12 on the PC3 - Achieved between 0 and 0.15%CO with 30-180 on the HC's.

But no matter what i seemed to do with the thing, couldnt get the Lambda to drop below 1.09 while the CO & HC were in limits.

To get the lambda correct the HC's were up near 3-400 and CO at 0.80-0.9. Everything was nice and warm! running for over half an hour at 2.5-3krpm. Its got me at a loss as it SVA'd first time 3 yrs ago. Unfortunatly i cant find the map i used. Only thing thats different this time is the cat, I cant see it being the cat though?

Any suggestions welcome as its winding me up now! If anyone has got an SVA map i can try i would be most appreaciative.

Its a '06 5VY with PC3, PX600 air box, MNR Headers and can.

Cheers

could be an air leak in the exhaust from those numbers. have you got the AIS valve still attached? that can let air in (even though it shouldn't once warm) and effect lambda. try blocking the pipe. lgot better readings with it connected though

The AIS is removed, the ports in the cam cover are blanked with threaded plugs - ive just checked these, all still intact and sealed. The old AIS pipes on the top are used for crankcase breathing.

The AIS was blanked off for SVA.

My only possible concern is the MNR can has riveted on end plates, which has always leaked a little around the rivets but this was the same at SVA and didnt cause a problem. So im somewhat at a loss!