Right, just been out to set the CO on Cosnada. Base idle all set, fuel pressure 3.5 bar (no vac and plugged) etc etc.

I only have a Gunson gas tester but I have used one for years to tweak stuff and they are ok.

I started out with an initial reading of 9.7 So, I'm tweaking the pot on the ECU (L8 Green top with lambda / CL enabled). I have managed to get the CO down to 4.6 at its lowest but can't get it any lower. It just starts creeping up if I adjust any more. I try a little opposite direction on the pot to try and find the 'middle sweet spot' but couldn't.

Is this indicative of a knackered lambda sensor as I was hoping to get it down to about 1.5 CO.

Suggestions?