I Had a peugeot 106 1.1 that had similar emissions. I checked and scoped everything i could, replaced inlet and exhaust manifold gaskets due to slight leaks, spark plugs and leads due to looking old and still emissions high. New lambda sensor also. In the end as a last resort i fitted a new cat, (cheepo one, £28 i think?) Emissions then were vertually down to zero! Didn't think a cat could bring it down that much but it did. So i'd defently try a new cat 1st.