[nikitopo]

I don't think you need any MAF rescaling. The ECU when it is in closed-loop mode, it takes additional measurements from the O2 sensor and adjusts the AFRs. These measurements are much more exact than the MAF measurements. This is because ECU expects to be able to deal with overly dirty fuel filters and reduced fuel flow issues. Then it also uses these corrections in the MAF readings in open-loop mode. In a sense, the ECU will somehow re-calibrate the MAF readings itself. It might not be perfect, but it will do the job. I would expect issues in the AFR, only if the MAF sensor needs a big re-calibration.