Only sure fire way is to check the sticker in the boot for the kW rating.
The badges on the back mean diddley squat I'm afraid
though in a perfect world the all red TDI means 150, Red Di means 130 and Red i means 115 or less...... All silver ones I think denote the SDI versions or if its an all silver GTI it should be an Anniversary model (you can verify this because it will be a 3door)
you do get to a point where you can spot a lesser model trying to be something it's not via the moudlings, wheels, bumpers etc
