I am pretty sure that the Co adjust on the ecu is only for idle speed, and has absolutely nothing to do with the rest of the map as far as I know.

If you are concerned about leaning off, you could either fit a lambda sensor and gauge, or else get on rollers. They will check the co always through the rev range.

Only slight word of warning - I put an air fuel ratio meter on mine, and it is completely useless after a good thrashing. I think the sensor overheats!

Hope this helps!!