High CO emissions on a Xantia again - V6 this time...

[andmcit]

I've taken on a very very very late s1 V6 (on a V plate) which shows 140k and has a gorgeous gearbox, interior etc etc
yet it was destined to be weighed in as it's failed the CO emissions on the MOT. It had LPG fitted to it but it wouldn't
run on gas as there was electrical issues with the installation - this has now been removed and there are currrntly
leaks on the inlet where the separate gas injectors were fitted. The car runs still although idle is high.

The HC figure is around 50-60 and the CO around 0.5-0.6 and I don't have the lambda figures (yet). The previous owner
has tried new spark plugs and it has a year old kitten converter as opposed to the proper fully grown cat which I do have
my doubts about. There were a few tiny leaks on the manifold that I hold the previous owner to seal which he did with
no difference in NOT readings and after reading the Citroenian about cat cleaner he tried that but with no success!

AFAIK it hadn't had a new lambda which I am seriously considering but are there any other ideas first or do I just jump
in and do that?

[jgra1]

I may have an es9 manifold And.. but not sure I can get it for a week or two..

[Timmo]

what fuel does he use???
wife lil fiat was up at 3% on co2, garage guys suggested a tank of good fuel and a Very spirited drive to clear it out, wife being no good at such driving, left it to me, put a tank of esso in over the local 'harvest fuels' station, drop of redex down the plug holes and plenty in the tank, and a Proper Hard drive for it on the way back to the mot station resulted in a drop of CO2 to .3% and a pass,
may be worth a thought??

[CitroJim]

Get it on a Lexia and check the MAP sensor and oxygen sensor. Don't randomly do things until you have been Lexia'd.

If it's idling high you have manifold air leaks.. Fix them.

The kitten may prevent a pass. You may have to get a proper one on there for the MOT. Those kittens are not up to the job.

Get the gas working. It'll then be tested as a non-cat. Problem solved.

What;s wrong with the gas anyway?