don't know proper; they look best pointing reverse
Have studied them both ways on my (former) E34M5 and
just my opinion but aesthetically they look much better 'pointing' in the backwards direction;
meaning- pointing counter-clockwise for the passenger side,
clockwise for driver side.
Since my car was a '91, I figured the purity aspect was already spoiled by adding TStars (oem were turbine covers), so I just went with most attractive config. Turbines served functional aerodynamic role, TStars probably much less so.