Dave, Is your cossie running vernier cam gears that are not at the standard settings ? or has the Cyl head been machined previously ?

The reason i ask is cos both of these will reduce the vacuum signal to the map sencor at idle beacause the stock cam timing has changed and the mapping in the chip was probably based on standard cam timing/vaccum. This will make the engine run richer than normal cos the ecu may think that there is load on the engine.

Here in Australia most of the cossies run the Autronic ecu. I have programmed a few cossies here in OZ and once we get the engine mapped, we then start playing with the cam timing and immediatly the mixtures at idle will go rich if vacuum is reduced (increased overlap) or lean if the vacuum is increased (reduced overlap). Obviously it just a matter of sorting the cam timing and then re adjusting the idle mixture to suit.

I know that as soon as green (803 or larger) injectors are fitted that the stock ecu does struggle to have a lean idle as we have seen this on all the "chipped" cossies here. Also the heat range of your spark plugs will effect the idle CO readings. Cold plugs will struggle compared to hot (standard) spark plugs when you are trying to reduce the idle CO's.

J