can the ECM/ECU be adjust for leaner fuel mixture during ignition, i.e. cold-start? I understand that at cold-start the fuel mixture is suppose to be rich to aid in starting. But I think my fuel mixture is too rich and the engine knocks on cold starts.

 

You have it backwards. Engine knocks are due to being lean, not rich.

 

ECU controls engine based on many sensors including MAF, O2, MAP, Intake Temp, Engine Coolant Temp, etc. It will adjust engine parameters based on input readings compared against ECU performance program.

The knocking you are hearing is more likely due to piston slap or valve noise, and may be the VVEL system which is known to make knocking noise - there was a TSB for 2008 models. Infiniti also will recommend their Ester oil if you have this issue.