[CSG Mike]

Originally Posted by tomm.brz

maf doesn t pick up all the airflow differences, specially if there are unexpected changes of volumetric efficiency
Also, it relies entirely to a pre-set scaling

Primary lambda is what catches AFR fluctuations
but the ecu must be in a closed loop mode (either stock logic, or ecutek CL fuel control) to take action and correct that AFR to follow the target

CSG Mike maybe forgot, but the master tuner of his company is already enabling closed loop mode all the time at all rpm

We are strictly referring to the factory tune.