Marlin: Not Working: Need different steps for dual extruder

I am actually facing a problem that I need different steps_per_unit for each extruder but unfortunately, Marlin only considers the first value of steps_per_unit given for extruders and operate both extruders according to that value.

it operates both extruders according to first given value {99} and don't consider the second value for second extruder {1320}
#define DEFAULT_AXIS_STEPS_PER_UNIT {87.5, 87.67, 2520.49, 99, 1320} // X,Y,Z,E0...

I am using // RAMPS 1.3 = 34 (Power outputs: Extruder0, Extruder1, Bed)

Looking forward to your response......