As far as I know, it's the stock drivetrain, non-XFi.
You can read about his mods & driving technique in this post:
http://ecomodder.com/forum/showthrea...html#post51737
And his garage entry is here:
Details: the metro experience (retired) - 1994 geo metro 4 dr HB Fuel Economy - EcoModder.com
Driving technique is the big contributor to his numbers. 2 most important tips noted:
1) his commute allows him to cruise at 45 mph or less
2) engine off as much as possible