punto emissions

I have a 1999 Punto 60S (old shape) which has been an excellent car during the four years I've owned it.
It drives well and returns about 40mpg in the Winter and 45mpg in the
Summer.
Each year it has sailed through it's MOT with no problems but I notice that each time the fast idle Lambda reading is only a borderline pass:
1.027 against a maximum allowable of 1.030 (the minimum is 0.970)
By my reckoning that's only a third of one percent inside the limit!
Other readings are very low:
HC: 2 (max allowed 200) CO: 0.00 (max allowed 00.30)
The car has covered 42000 miles (last year it had covered 33000 and gave very similar readings)
This all suggests to me the car is perhaps running a little 'richer' than ideal.
A few years ago I worked with Vauxhalls and one of the 'tweaks' you could do to lean off the mixture a little was to back off the throttle position sensor a little so that the engine management system thought that you were in less of a hurry!
Although it's a year to my next MOT I'd rather suss this one out well in advance - I don't want a fail and then an expensive trial and error exercise looking for the problem. Because I've had no real problemsI don't know how much local expertise there is around here when it comes to sorting out the tricky stuff!
Anybody got any ideas?
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I dont think you have a problem, HC and CO should both be 0 when the cat is hot. The value of lambda is not that important on the closed loop injection system fitted to the punto.
If you really want too change something you could always change the lambda sensor, since its operation degrades with time yours may have become lazy.
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