marlinfw.org/docs/gcode/M092.html
"Requires DISTINCT_E_FACTORS" - if the stock firmware did not activate this, you are lost.
I'm not sure weather T0 vs. T1 selects the first vs. second motor or weather T1 vs. T2 would be correct instead. Maybe M92 will print the current settings for both (write them down) before starting.
Be sure to measure with dismounted hotend and to store the settings to EEPROM by typing "M500". The steps per mm is a function of gear and motor times microsteps - you should not use it to compensate for the effect of the nozzle (as far as I learned).