co idle mixture - discussion

[Apsogos]

Good morning,
i want to ask about co idle mixture.
specs : 4age 16v european second generaton tvis engine.(no catalytic converter)
Freshly rebuilded.Before the rebuild the co mixture was set to about 1.38%

After the rebuild on 2000kms, i replace the fuel pump , i cleaned the injectors, i replace the igniter, fuel pump internal and external filter and i reset the ecu.

Now i have 3000kms.Few days before i went to my mechanic to check the CO and was at 6% !!!
a)how that happends?when i changed the fuel pump or cleaned the injectors maybe something changed?
b)We adjusted again the co to about 1.7% , here in Greece is a hot summer so the fan opened every minute at most at the procedure and was difficult to adjust right.
as the engine worked the co was moving from 1.20 to about 1.80.Is this right?meaning should it be stable as the engine working to a value ? eg to 1.5% ?

thank you