Ha, if you were closer, we could swap heads! I'm in Canada with a U.S. car and I have the opposite problem. Fortunately Canada used imperial units when I was a kid so I still know what 25 MPG means!
As you mentioned, it is not possible to change these other readouts.
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James now has: 2008 987S 6 speed
Crashed: 2010 987.2 pdk in speed yellow!
Sold to a cool racer chick: 2004 986 S
YouTube channel: the PORSCHE as seen by NewArt
www.youtube.com/channel/UCohdrH2xHTklM1thxk0KKOQ?