6 hrs in and out Kowloon from airport, may be a little tight. (45 min clear immigration and another 45 min immigration and security check)

The other option is take S1 bus (HK$3.5) to the near by Tung Chung City Gate (about 20-25 min), this is the last Metro stop.

http://en.wikipedia.org/wiki/Citygat...e:Citygate.JPG

http://en.wikipedia.org/wiki/Citygate