Garmin will only recognise the factory set of voice names that is why you need to rename the voice file to English_American_.vpn
How to install:
Save your original voice file or rename it.
Copy English_American_Borat_.vpn to Garmin/voice folder and rename it to English_American_.vpn
Change your voice settings
Settings >> Audio >> Voice >> American English
Enjoy new voice.
Here are the original English files
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