might be an aftermarket thing wired by previous owner in one of the v35...
I was like you, won't sell my coupe FTW, but in the end I gave up and traded my coupe for golf gti, and didn't regret it at all, but hey that's just me... 5dr hatchback is a lot more practical for me, so I can put a baby seat at the back. and fit those huge luggages overseas relatives always bring with them when I pick them up @ airport twice a year.... coupe just don't cut it anymore for my need, I always had to ask them if they had big luggage or not (in horror) when I had the v35 coupe.
golf's tank is only 55ltr compared to coupe's 65ltr but the golf took me 100km further from a tank fill... and dsg is a lot more fun than that conventional slushbox auto in my v35... quieter ride too and almost as quick.
and that nifty 3 blinker feature on lane change ;-)
on the golf it can be enabled/disabled through the on-dash user setting, very handy feature to have to personalise the way your car behave... they don't have it on the v35, and those navi screen, they only do trip computer, compass, and service reminder, there's no setting or menu option in there to set it. I know cos we now have the english translation software for those japanese menu for the 2001-2004 v35 (2005+ still in progress)