New Beetle Turbo diagnostic cable

Just spotted a comms cable on ebay sells for about $60 landed ..says you can use shareware to diagnoise ...modify??/ ..anyone had any experience with this set up..can you also use this to modify performance?
Thanks http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=4574685137&rd=1&sspagename=STRK%3AMEWA%3AIT&rd=1

You cant do anything with it but check and erase faults . The factory ECU only allows limiting values for performance gains . You have to know which channels they are anyway . This is not really a good tool unless you own a couple of cars and you tinker with them all the time .