I ve done similar tuning on same car with early ME7.5 with narrowband.
It needs more caution while tuning the fueling and someone who knows should do it.
Without injectors calibration (you run 4bar with s3 injectors), with maf unplugged etc it really make me think once more that 20VT are very tough cars
Yes ecu remapping is needed and i dont think there is a ready file for your car to flash it right away. You know how to flash it? Those ecu may be stubborn with nefmoto tool.