OK so its an A6 2.8 but no-one lives over there so I am asking here!
MOT at Kwikfit (yes I know, first mistake but they are £20 cheaper than anyone else so the retest is basically free!)
Lambda and CO failed but so unbelievably close to the limit!!
0.022 on lambda first fast idle
0.001 on lambda on second fast idle!
0.030 and 0.044% over on CO on fast idle tests
I have a small leak just before the CAT, that wouldn't change anything would it?
Going to log Lambda measuring blocks and voltage now and swap the plugs out
its very minor