I had the smaller 1.3 version centre console, until i upgraded, and i thought exactly the same. Got it from the scrap yard, put it in mine, had the weird extension, and took it back, put it back in the car to check, and it was the same, checked all the other GTIs and all the same. I finally realised it is there to direct the air from the heeater to the back footwells. On the smaller console, the heater channels are all blocked off, when i upgraded, i noticed all the extra channels (two on either side of the centre, and the two going under the console into the back)