480 2.0 high CO emissions - help please!

My 480 just failed it's MOT on:
Lower wishbone bushes (all 4 really) and both anti roll bar links at the rear - nothing difficult to diagnose, about £200 worth.

The real problem though is the CO emissions are too high, being about .7 @ idle and about 1.25 @ 2600 rpm.
The oxygen and HC levels are spot on.

My dad (lol don't think I'm a wipper snapper by that!) took the car to his local mechanic today to have it analyzed after putting some Forte gas test cleaner through (which helped with smoothness while driving so not a complete waste).
It's still running rich apparently, but to quote what they told him "sorry but we haven't a clue what's wrong".

They said the lambda sensor and cat seem to be working ok due to the oxygen and HC levels being right, but the car is just running too rich.

Driving is fine, idle, light and heavy throttle are all good.
No flat-spots, hesitation or any other abnormalities.

I thought it might be a MAF problem, but looking up the specs, the 2.0 engine doesn't appear to have one - is that true?
Any suggestions where/what to check?

I know I can measure the actual signal output from the lambda sensor, but don't know exactly where to attach the leads - maybe just before it enters the ecu?

Any other good suggestions?

Edit: Damn, forgot - the clip is missing from the hose that goes from the throttle body to what I think is the crackcase ventilator (canister thing down and left a bit) the clip is missing from the cansiter end. Could that cause this sort of problem? - Going to get a new clip anyway, but I'm not sure that's the culprit.

[Chris Wickers]

I had a similar problem.

After two weeks in a main dealer having tried absolutely everything the problem was diagnosed as the cambelt being one tooth out of alignment!

Hope this helps.

Chris