All things are difficult until you have done them
.
Took a deep breath and followed the instructions in the link:
www.advanced-incar.co.uk
My nervousness came from using a Chinese VCDS but it worked. No expert but believe you can do it with a Carista too. Would invite others to comment from a more knowledgable position.
Took a deep breath and followed the instructions in the link:
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VCDS How To - Activate Big Digital Speedo On MFD / DIS – MPH - Advanced In-Car Technologies
How To Remove KPH From Your Volkswagen Speedo And Replace It With A Digital MPH Speedo Using VCDS / VAG-COM. Suitable For Golf, T5, Scirocco etc!

My nervousness came from using a Chinese VCDS but it worked. No expert but believe you can do it with a Carista too. Would invite others to comment from a more knowledgable position.