Launch X431 X-prog3 programmer is very good at ECU/TCU cloning.  

Clone Mercedes VGS NAG3 Gearbox by Launch X431 IMMO Plus Success. 

Device required: 

Launch X431 X431 PAD VII/PAD V series or IMMO series tablet (IMMO PLUS/IMMO Elite/IMMO Pro)

Launch X-Prog3 programmer

Launch MCU3 adapter

Original VGS3 gearbox

New VGS3 gearbox need to replace

*To perform ECU/TCU cloning function with X-prog3 you should have X431 PAD or IMMO series tablets. X431 V/V+/Pros with X-prog3 won’t do ECU cloning.

Select IMMO Prog function

Connect X-PROG3 with IMMO Plus (connection instruction)

Select Gearbox->Benz->VGS-NAG3->View Wiring Diagram->Connect to MCU3 adapter plate
Connect VGS gearbox with X431 IMMO Plus tablet follow the wiring diagram
Connect Gearbox

Do a Backup full data

Read and save flash data
Disconnect old VGS NAG3 gearbox
Connect new VGS NAG3 gearbox need to be replaced

Backup full data of the new VGS NAG3

Select Restore complete data
Update original VGS data to restore

Make sure Bosch bumber of the new ECU is the same from that of the original ECU.

Write eeprom and flash to new VGS3
Then verify if the VIN code is the same.