2001 1.6.16v 1596 60k

Car has failed MOT on emissions, NO and CO both much to high on all tests.

Have replaced pre-cat Lambda but still reading as follows when car is warm:
pre-cat: open loop v0.014 bottom limit
post-cat: open loop v0.942 rich

2 years ago had replacement exhaust manifold for crack, last year had replacement exhaust, everything after the cat. Emissions have always been tricky and I think last year they may have passed it 'anyway' after changing exhaust

Car does not idle smoothly, idles to about 700 then either dies or 'catches' stall and revs right up.

Any suggestions on where to look next? Why isn't the emissions going closed loop? Is it because the readings are inappropriate for that? Is it worth trying changing the post cat sensor? What else could it be would clogged cat cause this? How about an air leak on the injection (throttle pot?) or exhaust sides? Garage last year also suggested it might need a new ECU

Thanks

No one have any suggestions?

How about a good service with a engine flush?
Also use forte diesel injector cleaner and drive it hard and see if improves?
When was last time you changed fuel filter and serviced car?

Why diesel injector cleaner on a petrol?
NO is produced at higher temperatures (suggesting lean burn) while CO is produced as a result of insufficient oxygen in the burn (rich mixture) which is a bit of a paradox.
Can't see an engine flush helping this, faulty lambda looks like a good shout.